Question

Geometry help please ;(

Answer 1

The answer would be a reason being sinangle= opposite/hypotenuse
if u shift ur phone and observe it is 12/13

Answer 2

You know this is a right angled triangle. so you can use SOH CAH TOA.
taking <A as the angle you want to find. you can use any of the above with H,O or A . 
using sine : ur opposite is 12 ( the side opposite the <A) , your H is your hypotenuse(longest side) aka 13. 
Thus 
sine<A = 12/13 
OPTION A