Question

Use an identity to find the value of

Answer 1

sin Ф.

Explanation:

Cos (-270) = cos 90 = 0 and sin(-270) = sin 90 = 1.

So cos ( Ф - 270) = cos Ф cos (-270) + sin Ф sin(-270)

= cos Ф * 0 + sin Ф * 1

= sin Ф.