Trigonometry Examples

$\cos (x + y)$

Step 1

Use the sum formula for cosine to simplify the expression. The formula states that $\cos (A + B) = - (\cos (A) \cos (B) + \sin (A) \sin (B))$ .

$\cos (y) \cdot \cos (x) - \sin (y) \cdot \sin (x)$

Step 2

Remove parentheses.

$\cos (y) \cdot \cos (x) - \sin (y) \cdot \sin (x)$