Question

choose the correct ratio. cos⁻¹(20/9) sin⁻¹(9/20) cos⁻¹(9/20) tan⁻¹(9/20)

Explanation:

Step1: Recall cosine - ratio definition

In a right - triangle, $\cos\theta=\frac{\text{adjacent}}{\text{hypotenuse}}$. Here, for angle $x$, the adjacent side to angle $x$ is 9 and the hypotenuse is 20. So, $\cos x=\frac{9}{20}$, then $x = \cos^{-1}(\frac{9}{20})$.

Answer:

C. $\cos^{-1}(9/20)$