Use the properties of the trigonometric functions to find the exact value, without using a calculator

Question

4 cos^(2) 78 degrees + 4 sin ^(2) 78 degrees

Answer 1

Hi Joseph R.,

Using the identity sin²θ + cos²θ = 1:

4*cos²(78^o) + 4*sin²(78^o) = 4*[cos²(78^o) + sin²(78^o)] = 4*[1] = 4.

I hope this helped, Joe.