Verifying identity plz helpp!
cos(x+y) + cos(x-y) = 2cosx cosy

2cosx cosy = 2cosx cosy

Step-by-step explanation:

cos(x+y) + cos(x-y) = 2cosx cosy

Use the formula for "Functions of the sum of two angles" and the "Function of the Difference of Two Angles" and substitute that in.

(Cosx cosy - sinx siny) + (cosx cosy + sinx siny)

Drop the parentheses

Cosx cosy - sinx siny + cosx cosy + sinx siny

Sinx siny can cancel

Cosx cosy + cosx cosy

This can be simplified to

2cosx cosy

  70 square units

Step-by-step explanation:

The spreadsheet is attached.

It shows the area of the trapezoidal shape to be 70 square units.