Question

On a piece of paper draw and label a right triangle using the given sides, solve for the unknown side and write the trigonometric functions for angles A and B, if a=5 and c=7.

I already found side b which equals 2 sqrts of 6.
Now I need to find the sin A and cos A. I know that sin is opposite/hypotenuse and cos is adjacent / hypotenuse. That’s as far as I can get however, I am provided with choices;

Sin A
a)7/5
b)2sqrt6/7
c)7/2sqrt6
d)5/7

Cos A

a)7/5
b)7/2sqrt6
c)2sqrt6/7
d)5/7

Please help!!!


So why not use for sine the value of a/c, and for cosine, b/c ?