Question

in right triangle ABC, m∠C = 90°. if cos B = 5/13, which function also equals 5/13?

Answer 1

answer is Sin A = 5/13 

Answer 2

In $\Delta ABC$, $C=90^o$. Therefore,

$A+B=90^o\\ B=90^o-A$.

Also $\cos B=\frac{5}{13} \\ \cos (90^o-A)=\frac{5}{13} \\ \sin A=\frac{5}{13}$.

Thus, $\sin A$ equals the given fraction.