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