Question

If 0° ≤ θ ≤ 90° and cosθ = 11 15 , what is the value of sin (90° - θ)?

Answer 1

Since the angles θ and 90° - θ are complementary, the cosine of one of the angles is equal to the sine of the other. Therefore, because cosθ = $\frac{11}{15}$, the value of sin (90° - θ) must be $\frac{11}{15}$.

Answer 2

The same value as cosα

cosα=sin(90-α) and vice versa

sinα=cos(90-α)