Sum and Difference Formulas in Trigonometry

1. sin(x + y) = sin x * cos y + cos x * sin y
   
   
2. cos(x + y) = cos x * cos y - sin x * sin y
   
   
3. tan(x + y) = [tan x + tan y] / [1 - tanx * tany]

Difference Formulas

1. sin(x - y) = sin x * cos y - cos x * sin y
   
   
2. cos(x - y) = cos x * cos y + sin x * sin y
   
   
3. tan(x - y) = [tan x - tan y] / [1 + tanx * tany]