Krishna
0

Step 1: Recall the complimentary angles relation.

THEOREM: If \angle A \text{ and } \angle B are the acute angles of a  right triangle,

sin A = cos B

EXAMPLE: 90°–x and x are complementary, since their angles sum to 90°.

So, the cosine of 90°–x is equal to the sine of x.

\cos(90 - x) = \sin(x) = -0.9