A Level Maths Practice Questions with Solutions
Welcome to our curated collection of Advanced Level (A-Level) Mathematics questions. These multi-part problems are designed to challenge your structural understanding across core algebra, coordinate geometry, calculus, and trigonometry. Detailed analytical and graphical proof breakdowns are provided below.
Coordinate Geometry & Functions
Question 1 — Circle Properties
A circle has the equation \( x^2-4x+y^2+6y = 12 \) and center \( C \).
Show Step-by-Step Solution
(a) & (b) Converting to Standard Form:
To identify geometric properties of circles, reorganize the equation into the standard form: \[ (x-h)^2 + (y-k)^2 = r^2 \] where \( (h,k) \) matches the center, and \( r \) represents the radius. Complete the square independently for both variables:
\[ (x^2 - 4x) + (y^2 + 6y) = 12 \] \[ \left[(x-2)^2 - 4\right] + \left[(y+3)^2 - 9\right] = 12 \] \[ (x-2)^2 + (y+3)^2 = 12 + 4 + 9 \] \[ (x-2)^2 + (y+3)^2 = 25 \quad \text{--- (Equation I)} \]
Extract parameters by direct comparison with our standard template:
- \( r^2 = 25 \implies r = 5 \) units.
- Area: \( \pi r^2 = 25\pi \) square units.
- Center (b): The coordinates of center \( C \) are \( (2, -3) \).
(c) Determining Coordinates of Endpoint B:
Because line segment \( AB \) constitutes a geometric diameter, the circle's center \( C(2,-3) \) serves explicitly as the midpoint of endpoints \( A(6,-6) \) and \( B(x_0, y_0) \). Use the midpoint theorem:
\[ \dfrac{x_0 + 6}{2} = 2 \implies x_0 + 6 = 4 \implies x_0 = -2 \] \[ \dfrac{y_0 - 6}{2} = -3 \implies y_0 - 6 = -6 \implies y_0 = 0 \]
The coordinates for diametric opposite point \( B \) are \( (-2, 0) \).
Question 2 — Trigonometric Proof
Prove the identity: \[ \dfrac{ 2 \cos x + \sin (2x)}{2\sin x + 2 \sin^2 x} = \cot x \]
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We work from the more complex Left-Hand Side (LHS) and resolve to the Right-Hand Side (RHS) through identity substitution.
Step 1: Expand compound angles. Substitute the double-angle identity \( \sin(2x) = 2\sin x\cos x \) directly into the numerator expression:
\[ \text{LHS} = \dfrac{ 2 \cos x + 2 \sin x \cos x}{2\sin x + 2 \sin^2 x} \]
Step 2: Factor algebraic groups. Pull out structural common factors in both halves of the fraction bar (\( 2\cos x \) up top, \( 2\sin x \) below):
\[ \text{LHS} = \dfrac{ 2 \cos x (1 + \sin x)}{2 \sin x (1 + \sin x)} \]
Step 3: Simplify. Given \( 1 + \sin x \neq 0 \), eliminate matching scalar fractions and components across boundaries:
\[ \text{LHS} = \dfrac{\cos x}{\sin x} = \cot x = \text{RHS} \quad \blacksquare \]
Question 3 — Polynomial Rationality & Exponentials
The function \( f \) is modeled by \( f(x) = x^3-2x^2-5x+6 \). Its cubic curve crosses the x-axis precisely at \( x = 1 \).
Show Step-by-Step Solution
(a) Factoring the Cubic Equation:
Since \( f(1) = 0 \), the factor theorem dictates that \( (x - 1) \) acts as a structural factor of the expression. Use polynomial division to reduce degrees:
\[ \dfrac{x^3 - 2x^2 - 5x + 6}{x - 1} = x^2 - x - 6 \]
Factor the resultant quadratic expression by finding values summing to \( -1 \) that yield a product of \( -6 \) (\(-3\) and \(2\)):
\[ x^2 - x - 6 = (x - 3)(x + 2) \]
Thus, written completely as linear products: \( f(x) = (x - 1)(x - 3)(x + 2) \).
(b) Finding the Roots:
Set linear product partitions cleanly to zero: \( (x - 1)(x - 3)(x + 2) = 0 \).
Solutions: \( x = 1, \; x = 3, \; x = -2 \).
(c) Transforming the Exponential Equation:
Analyze reciprocal properties to clarify exponential states: rewrite \( \frac{5}{e^{2x}} \) as \( 5e^{-2x} \). The entire sequence reads: \[ e^{-6x} - 2e^{-4x} - 5e^{-2x} + 6 = 0 \]
Define a dummy variable mapping parameters: let \( z = e^{-2x} \). Squaring gives \( z^2 = e^{-4x} \) and cubing yields \( z^3 = e^{-6x} \). Substitute these in:
\[ z^3 - 2z^2 - 5z + 6 = 0 \]
This matches our exact cubic template solved during part (b). Thus, possible values for \( z \) are \( 1, 3, \) or \( -2 \). Re-evaluate back to structural variables:
- \( e^{-2x} = 1 \implies -2x = \ln(1) \implies x = 0 \)
- \( e^{-2x} = 3 \implies -2x = \ln(3) \implies x = -\dfrac{\ln 3}{2} \approx -0.5493 \)
- \( e^{-2x} = -2 \implies \) No real solutions, since real natural exponents remain strictly positive (\( e^{-2x} > 0 \)).
Final Real Solution Set: \( \left\{ 0, \; -\dfrac{\ln 3}{2} \right\} \).
Trigonometric Identities & Equations
Question 4 — Trigonometric Form Conversions
\( 4 - 2 \left( \cos (2x) + 1\right) + 2(\sqrt{2} - 1) \sin x - \sqrt{2} = 0 \) over the periodic interval \( [0, 2\pi) \).
Show Step-by-Step Solution
(a) Solving the Quadratic Equation:
Solve via the quadratic formula where \( a = 1, \; b = \frac{\sqrt{2}-1}{2}, \; c = -\frac{\sqrt{2}}{4} \):
\[ \Delta = b^2 - 4ac = \left(\frac{\sqrt{2}-1}{2}\right)^2 - 4(1)\left(-\frac{\sqrt{2}}{4}\right) \] \[ \Delta = \frac{2 - 2\sqrt{2} + 1}{4} + \frac{4\sqrt{2}}{4} = \frac{3 + 2\sqrt{2}}{4} = \left(\frac{\sqrt{2}+1}{2}\right)^2 \]
Extract roots tracking radical changes cleanly:
\[ x = \dfrac{-\frac{\sqrt{2}-1}{2} \pm \frac{\sqrt{2}+1}{2}}{2} \] \[ x_1 = \dfrac{1}{2}, \quad x_2 = -\dfrac{\sqrt{2}}{2} \]
(b) Proving the Double-Angle Statement:
Recall standard cosine double-angle transformations: \( \cos(2x) = 1 - 2\sin^2 x \). Substitute directly into our standard formulation:
\[ \text{LHS} = \cos(2x) + 1 = (1 - 2\sin^2 x) + 1 = 2 - 2\sin^2 x = \text{RHS} \quad \blacksquare \]
(c) Analyzing the Transformed Periodic Equation:
Substitute our part (b) verified identity into the compound problem structure:
\[ 4 - 2(2 - 2\sin^2 x) + 2(\sqrt{2}-1)\sin x - \sqrt{2} = 0 \] \[ 4 - 4 + 4\sin^2 x + 2(\sqrt{2}-1)\sin x - \sqrt{2} = 0 \] \[ 4\sin^2 x + 2(\sqrt{2}-1)\sin x - \sqrt{2} = 0 \]
Divide down completely by structural factor \( 4 \) to establish standard structures:
\[ \sin^2 x + \dfrac{\sqrt{2}-1}{2}\sin x - \dfrac{\sqrt{2}}{4} = 0 \]
Let \( z = \sin x \). The equation perfectly tracks the quadratic structural baseline solved during part (a). Hence:
\[ \sin x = \dfrac{1}{2} \quad \text{or} \quad \sin x = -\dfrac{\sqrt{2}}{2} \]
Evaluate these within domain requirements across periodic loops \( [0, 2\pi) \):
- \( \sin x = \frac{1}{2} \implies x = \dfrac{\pi}{6}, \; \dfrac{5\pi}{6} \)
- \( \sin x = -\frac{\sqrt{2}}{2} \implies x = \dfrac{5\pi}{4}, \; \dfrac{7\pi}{4} \)
Combined Solution Set: \( \left\{ \dfrac{\pi}{6}, \; \dfrac{5\pi}{6}, \; \dfrac{5\pi}{4}, \; \dfrac{7\pi}{4} \right\} \).
Question 5 — Graphing Sine Variations
Show Step-by-Step Solution
(a) Graphing Key Periodic Loops:
The standard period for transformations sizing systems scales explicitly: \( T = \frac{2\pi}{2} = \pi \). Calculate values across core structural intervals:
| \( x \) | \( 0 \) | \( \frac{\pi}{4} \) | \( \frac{\pi}{2} \) | \( \frac{3\pi}{4} \) | \( \pi \) |
|---|---|---|---|---|---|
| \( \sin(2x) \) | \( 0 \) | \( 1 \) | \( 0 \) | \( -1 \) | \( 0 \) |
(b) Solving the Exact Statement:
Evaluate trigonometric properties directly over scaling angles: \[ \sin(2x) = \dfrac{1}{2} \implies 2x = \dfrac{\pi}{6} + 2k\pi \quad \text{or} \quad 2x = \dfrac{5\pi}{6} + 2k\pi \]
Isolate structural metrics inside the domain parameters \( [0, \pi) \): \( x = \dfrac{\pi}{12} \) and \( x = \dfrac{5\pi}{12} \).
(c) Resolving Inequalities Dynamically:
Isolate algebraic entities: \( \frac{1}{2} + \sin(2x) \ge 1 \implies \sin(2x) \ge \dfrac{1}{2} \).
By mapping boundaries from our exact values evaluated in part (b), the sine function remains strictly above the threshold level between its entry and exit intersections.
Interval Output: \( \left[ \dfrac{\pi}{12}, \; \dfrac{5\pi}{12} \right] \).
Polynomial Analysis & Inverse Functions
Question 6 — Composite Functional Roots
Function \( f \) has fixed zeros at \( x = 1 \) and \( x = -3 \). Identify the structural roots for the compound polynomial expression: \[ f(-2x^2 + x + 3) \]
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A composite function evaluates to zero if and only if its inner argument matches an established root of the base function. Thus, the inner polynomial must equal either \( 1 \) or \( -3 \).
Case 1: Evaluate argument matching the root at 1:
\[ -2x^2 + x + 3 = 1 \implies 2x^2 - x - 2 = 0 \] \[ x = \dfrac{-(-1) \pm \sqrt{(-1)^2 - 4(2)(-2)}}{2(2)} = \dfrac{1 \pm \sqrt{17}}{4} \]
Case 2: Evaluate argument matching the root at -3:
\[ -2x^2 + x + 3 = -3 \implies 2x^2 - x - 6 = 0 \] \[ (2x + 3)(x - 2) = 0 \implies x = -\dfrac{3}{2}, \quad x = 2 \]
Combined Solution Set for structural composite zeros: \( \left\{ -\dfrac{3}{2}, \; 2, \; \dfrac{1 - \sqrt{17}}{4}, \; \dfrac{1 + \sqrt{17}}{4} \right\} \).
Question 7 — Factor Theorem & Curves
Function \( f \) is defined by \[ f(x) = x^4 + ax^3 + bx^2 + 4 \]
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(a) Tracking Simultaneous Coefficient Equations:
Apply the factor theorem: set intercept coordinates directly to zero values.
\[ f(1) = 0 \implies 1 + a + b + 4 = 0 \implies a + b = -5 \] \[ f(-1) = 0 \implies 1 - a + b + 4 = 0 \implies -a + b = -5 \]
Adding the simultaneous linear pairs isolates the constants cleanly: \( 2b = -10 \implies b = -5 \). Substituted back, it resolves to \( a = 0 \). Therefore, parameters are \( a = 0, \; b = -5 \).
(b) Complete Factorization Breakdown:
Substitute calculated metrics to reveal the true polynomial expression: \[ f(x) = x^4 - 5x^2 + 4 \]
This expression functions as a quadratic in terms of \( x^2 \). Factoring directly yields:
\[ f(x) = (x^2 - 1)(x^2 - 4) \]
Apply difference-of-squares expansions across both quadratic groups to find the linear products: \( f(x) = (x - 1)(x + 1)(x - 2)(x + 2) \).
Curve Analysis: Because the function features purely even exponents (\( f(-x) = f(x) \)), the graph exhibits perfect reflectional symmetry across the vertical y-axis. The curve crosses the horizontal boundary at \( \pm 1 \) and \( \pm 2 \), intercepts the vertical axis at \( (0, 4) \), and rises infinitely on both outer limbs due to its positive leading quartic term.
Question 8 — Systems of Circles
Two circles centered respectively at \( C_1 \) and \( C_2 \) have equations \( x^2 + (y-2)^2 = 16 \) and \( (x+1)^2 + y^2 = 9 \), intersecting at coordinates \( A \) and \( B \).
Identify coordinate intersections \( M \) representing the meeting point of the line through intersections \( AB \) and the line mapping center tracking paths \( C_1 C_2 \).
Show Step-by-Step Solution
Step 1: Isolate the radical line passing through AB. Expand both expressions completely to eliminate quadratic groupings:
\[ \text{Circle 1: } x^2 + y^2 - 4y + 4 = 16 \implies x^2 + y^2 - 4y = 12 \] \[ \text{Circle 2: } x^2 + 2x + 1 + y^2 = 9 \implies x^2 + y^2 + 2x = 8 \]
Subtract the second simplified equation from the first to eliminate quadratic terms: \[ (x^2 + y^2 - 4y) - (x^2 + y^2 + 2x) = 12 - 8 \]
\[ -2x - 4y = 4 \implies y = -\dfrac{1}{2}x - 1 \quad \text{--- (Line Equation I)} \]
Step 2: Find the line tracing center points C1 to C2. Extract coordinate values from the standard circle equations: center \( C_1 = (0, 2) \) and center \( C_2 = (-1, 0) \). Determine the slope gradient:
\[ m = \dfrac{2 - 0}{0 - (-1)} = 2 \]
Using point-slope form with \( C_2(-1,0) \), the linear tracking equation is: \[ y - 0 = 2(x + 1) \implies y = 2x + 2 \quad \text{--- (Line Equation II)} \]
Step 3: Solve the simultaneous system for point M. Equate Equation I and Equation II:
\[ 2x + 2 = -\dfrac{1}{2}x - 1 \implies \dfrac{5}{2}x = -3 \implies x = -\dfrac{6}{5} \] \[ y = 2\left(-\dfrac{6}{5}\right) + 2 = -\dfrac{12}{5} + \dfrac{10}{5} = -\dfrac{2}{5} \]
Intersection coordinates for point \( M \) are \( \left( -\dfrac{6}{5}, \; -\dfrac{2}{5} \right) \).
Question 9 — Designing Inverses
Let \( g(x) = \sqrt{x^2-2x-3} \).
Show Step-by-Step Solution
(a) Radicand Restructuring:
Halve the linear parameter value, square it, and insert balance elements to complete the square: \[ x^2 - 2x - 3 = (x - 1)^2 - 1 - 3 = (x - 1)^2 - 4 \]
(b) Tracking Inverse Algebra:
Equate the target variable to the restructured functional statement, then swap variables to solve for the inverse relation:
\[ x = \sqrt{(y - 1)^2 - 4} \]
Square both sides and isolate the squared term containing \( y \):
\[ x^2 = (y - 1)^2 - 4 \implies (y - 1)^2 = x^2 + 4 \]
Take the square root of both sides, noting the dual sign possibilities: \[ y - 1 = \pm\sqrt{x^2 + 4} \implies y = 1 \pm\sqrt{x^2 + 4} \]
Since our primary definition enforces domain rules where variables remain restricted above critical limits (\( x \ge 3 \)), the inverse function must map onto outputs greater than or equal to 3. Therefore, select the positive root option:
\[ g^{-1}(x) = 1 + \sqrt{x^2 + 4} \]
(c) Deducing the Range:
By the fundamental definitions of inverse relationships, the range of an inverse function \( g^{-1} \) is identically equal to the domain constraints of its parent function \( g \).
Range Output: \( [3, \; \infty) \).
Calculus, Derivatives & Integration
Question 10 — Implicit Differentiation
A conic curve tracks algebraic configurations structured by: \( -2x^2 + 3y^2 - 2x = 1 \). Identify coordinates for all points exhibiting horizontal tangent behavior (\( \dfrac{dy}{dx} = 0 \)).
Show Step-by-Step Solution
Step 1: Take derivatives across boundaries implicitly. Differentiate both sides with respect to \( x \), applying the chain rule to the terms containing \( y \):
\[ \dfrac{d}{dx}(-2x^2 + 3y^2 - 2x) = \dfrac{d}{dx}(1) \]
\[ -4x + 6y\left(\dfrac{dy}{dx}\right) - 2 = 0 \]
Step 2: Substitute the target condition. To find horizontal tangents, set \( \frac{dy}{dx} = 0 \):
\[ -4x - 2 = 0 \implies x = -\dfrac{1}{2} \]
Step 3: Solve for the corresponding y-coordinates. Substitute \( x = -\frac{1}{2} \) back into the original curve equation to find the valid points on the graph:
\[ -2\left(-\dfrac{1}{2}\right)^2 + 3y^2 - 2\left(-\dfrac{1}{2}\right) = 1 \] \[ -2\left(\dfrac{1}{4}\right) + 3y^2 + 1 = 1 \implies -\dfrac{1}{2} + 3y^2 = 0 \] \[ 3y^2 = \dfrac{1}{2} \implies y^2 = \dfrac{1}{6} \implies y = \pm\sqrt{\dfrac{1}{6}} \]
The target coordinates matching horizontal boundaries are \( \left(-\dfrac{1}{2}, \; \sqrt{\dfrac{1}{6}}\right) \) and \( \left(-\dfrac{1}{2}, \; -\sqrt{\dfrac{1}{6}}\right) \).
Question 11 — Linear Trig Simplifications
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(a) Difference Identity Expansion:
Apply the sine difference identity \( \sin(A - B) = \sin A\cos B - \cos A\sin B \):
\[ \sin\left(x - \dfrac{\pi}{3}\right) = \sin x \cos\dfrac{\pi}{3} - \cos x \sin\dfrac{\pi}{3} \]
Substitute known exact values (\( \cos\frac{\pi}{3} = \frac{1}{2}, \; \sin\frac{\pi}{3} = \frac{\sqrt{3}}{2} \)):
\[ \sin\left(x - \dfrac{\pi}{3}\right) = \dfrac{1}{2}\sin x - \dfrac{\sqrt{3}}{2}\cos x \]
(b) Reorganizing Linear Equations:
Equate definitions across core terms:
\[ 2\sin x + 3\cos x = \dfrac{1}{2}\sin x - \dfrac{\sqrt{3}}{2}\cos x \]
Group matching variable sets on opposite sides of the equation:
\[ 2\sin x - \dfrac{1}{2}\sin x = -3\cos x - \dfrac{\sqrt{3}}{2}\cos x \] \[ \dfrac{3}{2}\sin x = \left( -3 - \dfrac{\sqrt{3}}{2} \right)\cos x \]
(c) Evaluating Exact Intercept Metrics:
Divide by \( \cos x \) to form a tangent expression, then solve for \( x \):
\[ \tan x = \dfrac{-3 - \frac{\sqrt{3}}{2}}{\frac{3}{2}} = -2 - \dfrac{\sqrt{3}}{3} \approx -2.5774 \]
Find the primary reference solution via the arctangent function: \[ x = \arctan(-2.5774) \approx -1.20 \text{ radians} \]
Add periodic iterations of \( \pi \) to find the valid values within our domain requirement \( [0, 2\pi) \):
- \( x_1 = -1.20 + \pi \approx \mathbf{1.94} \text{ rad} \)
- \( x_2 = -1.20 + 2\pi \approx \mathbf{5.08} \text{ rad} \)
Question 12 — Integration by Parts
Show Step-by-Step Solution
(a) Double-Angle Identity Manipulation:
Combine the double-angle formula with the fundamental Pythagorean identity to isolate the squared sine term:
\[ \cos(2x) = \cos^2 x - \sin^2 x = (1 - \sin^2 x) - \sin^2 x = 1 - 2\sin^2 x \]
Rearranging the equation yields the standard power-reducing identity: \( \sin^2 x = \dfrac{1 - \cos(2x)}{2} \).
(b) Evaluating the Definite Integral:
Substitute the identity from part (a) into the integral expression and split it into two distinct components:
\[ I = \int_0^{\pi} x \left( \dfrac{1 - \cos(2x)}{2} \right) dx = \dfrac{1}{2}\int_0^{\pi} x dx - \dfrac{1}{2}\int_0^{\pi} x \cos(2x) dx \]
The first linear integral evaluates directly via the power rule:
\[ \dfrac{1}{2}\left[ \dfrac{x^2}{2} \right]_0^{\pi} = \dfrac{\pi^2}{4} \]
Solve the remaining product integral using Integration by Parts for the section \( \int_0^{\pi} x \cos(2x) dx \):
Let \( u = x \implies u' = 1 \). Let \( v' = \cos(2x) \implies v = \dfrac{1}{2}\sin(2x) \).
\[ \int_0^{\pi} x \cos(2x) dx = \left[ \dfrac{1}{2}x\sin(2x) \right]_0^{\pi} - \int_0^{\pi} \dfrac{1}{2}\sin(2x) dx \] \[ = \left[ \dfrac{1}{2}x\sin(2x) \right]_0^{\pi} - \left[ -\dfrac{1}{4}\cos(2x) \right]_0^{\pi} \]
Evaluating this boundary set from \( 0 \) to \( \pi \) results in a net value of zero, as shown below:
\[ \left(0 - 0\right) + \left( \dfrac{1}{4}\cos(2\pi) - \dfrac{1}{4}\cos(0) \right) = \dfrac{1}{4}(1) - \dfrac{1}{4}(1) = 0 \]
Combining the results from both components yields the final evaluated value: \( I = \dfrac{\pi^2}{4} \).
Question 13 — Area Between Curves
Determine the precise vertical shift constant \( k \) such that the bounded region between the curves shown below evaluates to an area exactly equal to \( 5 \).
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The region is bounded above by the parabola \( y_{top} = x^2 + k \) and below by the line \( y_{bottom} = x - 1 \), spanning the interval from \( x = 1 \) to \( x = 2 \). Set up the area integral:
\[ A = \int_1^2 \left( (x^2 + k) - (x - 1) \right) dx \] \[ A = \int_1^2 (x^2 - x + k + 1) dx \]
Integrate each term using the power rule:
\[ A = \left[ \dfrac{1}{3}x^3 - \dfrac{1}{2}x^2 + (k + 1)x \right]_1^2 \]
Evaluate the expression at the upper bound (\( x = 2 \)) and subtract the evaluation at the lower bound (\( x = 1 \)):
\[ \text{At } x=2: \quad \dfrac{8}{3} - 2 + 2k + 2 = 2k + \dfrac{8}{3} \] \[ \text{At } x=1: \quad \dfrac{1}{3} - \dfrac{1}{2} + k + 1 = k + \dfrac{5}{6} \] \[ A = \left(2k + \dfrac{8}{3}\right) - \left(k + \dfrac{5}{6}\right) = k + \dfrac{11}{6} \]
Set the evaluated area expression equal to the target value of 5 and solve for \( k \):
\[ k + \dfrac{11}{6} = 5 \implies k = 5 - \dfrac{11}{6} = \dfrac{19}{6} \]
Question 14 — Derivative from First Principles
Use the formal limit definition of a derivative (first principles) to evaluate \( \sin'\left(\dfrac{\pi}{4}\right) \).
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The first-principles definition of a derivative states: \[ f'(x) = \lim_{h \to 0} \dfrac{f(x+h) - f(x)}{h} \]
Substitute \( f(x) = \sin x \) and evaluate at the target point \( x = \dfrac{\pi}{4} \):
\[ \sin'\left(\dfrac{\pi}{4}\right) = \lim_{h \to 0} \dfrac{\sin\left(\frac{\pi}{4}+h\right) - \sin\left(\frac{\pi}{4}\right)}{h} \]
Expand the compound angle in the numerator using the sine addition identity:
\[ \sin\left(\frac{\pi}{4}\right)\cosh + \cos\left(\frac{\pi}{4}\right)\sinh - \sin\left(\frac{\pi}{4}\right) \]
Reorganize and split the expression into two standard trigonometric limits:
\[ = \sin\left(\dfrac{\pi}{4}\right) \lim_{h \to 0} \left(\dfrac{\cos h - 1}{h}\right) + \cos\left(\dfrac{\pi}{4}\right) \lim_{h \to 0} \left(\dfrac{\sin h}{h}\right) \]
Apply the fundamental geometric limit theorems: \( \lim_{h \to 0} \frac{\sin h}{h} = 1 \) and \( \lim_{h \to 0} \frac{\cos h - 1}{h} = 0 \).
\[ \sin'\left(\dfrac{\pi}{4}\right) = \sin\left(\dfrac{\pi}{4}\right) \cdot (0) + \cos\left(\dfrac{\pi}{4}\right) \cdot (1) = \cos\left(\dfrac{\pi}{4}\right) = \dfrac{\sqrt{2}}{2} \]
Question 15 — Reciprocal Chain Rule Integration
Show Step-by-Step Solution
(a) Derivative and Integral Framework:
Differentiate \( f(x) = [u(x)]^{-1} \) using the power and chain rules:
\[ f'(x) = -1[u(x)]^{-2} \cdot u'(x) = -\dfrac{u'(x)}{u^2(x)} \]
Integrating both sides yields the corresponding integration template:
\[ \int \dfrac{u'(x)}{u^2(x)} dx = -\dfrac{1}{u(x)} + C \]
(b) Applying the Template to the Core Integral:
Reorganize the given integral to match the structural template found in part (a):
\[ \int_2^4 \dfrac{1}{x \ln^2 x} dx = \int_2^4 \dfrac{\left(\frac{1}{x}\right)}{(\ln x)^2} dx \]
Let \( u(x) = \ln x \), which implies its derivative is exactly \( u'(x) = \frac{1}{x} \). This fits the pattern perfectly. Integrate using the template:
\[ \int_2^4 \dfrac{u'(x)}{u^2(x)} dx = \left[ -\dfrac{1}{\ln x} \right]_2^4 = \left( -\dfrac{1}{\ln 4} \right) - \left( -\dfrac{1}{\ln 2} \right) \]
Simplify the result using the logarithm power rule, noting that \( \ln 4 = \ln(2^2) = 2\ln 2 \):
\[ = -\dfrac{1}{2\ln 2} + \dfrac{1}{\ln 2} = \dfrac{-1 + 2}{2\ln 2} = \dfrac{1}{2\ln 2} \]
Question 16 — Circular Tangents
Find all coordinates on the circle with a radius of \( 2 \) and centered at \( (3,-1) \) where the tangent line has a slope exactly equal to \( 2 \).
Show Step-by-Step Solution
Step 1: Write the circle's equation and find its derivative. Write the standard equation using the given radius and center, then differentiate implicitly:
\[ (x-3)^2 + (y+1)^2 = 4 \quad \text{--- (Equation I)} \]
\[ 2(x-3) + 2(y+1)\dfrac{dy}{dx} = 0 \implies (x-3) + (y+1)\dfrac{dy}{dx} = 0 \]
Step 2: Substitute the target slope condition. Set the derivative equal to the desired slope, \( \frac{dy}{dx} = 2 \):
\[ (x-3) + 2(y+1) = 0 \implies (x-3) = -2(y+1) \quad \text{--- (Equation II)} \]
Step 3: Solve the simultaneous system. Substitute the expression for \( (x-3) \) from Equation II back into Equation I:
\[ \left(-2(y+1)\right)^2 + (y+1)^2 = 4 \] \[ 4(y+1)^2 + (y+1)^2 = 4 \implies 5(y+1)^2 = 4 \] \[ (y+1)^2 = \dfrac{4}{5} \implies y+1 = \pm\dfrac{2}{\sqrt{5}} \implies y = -1 \pm\dfrac{2}{\sqrt{5}} \]
Find the corresponding x-coordinates by substituting these y-values back into Equation II:
\[ x - 3 = -2\left(\pm\dfrac{2}{\sqrt{5}}\right) \implies x = 3 \mp \dfrac{4}{\sqrt{5}} \]
The two points on the circle with a tangent slope of 2 are:
\( \left(3 - \dfrac{4}{\sqrt{5}}, \; -1 + \dfrac{2}{\sqrt{5}}\right) \) and \( \left(3 + \dfrac{4}{\sqrt{5}}, \; -1 - \dfrac{2}{\sqrt{5}}\right) \).