Question

∠A is an acute angle in a right triangle. Given that cosA=12/13, what is the ratio for sinA?

Answer 1

SinA=5/13
if it is a right triangle we can use the Pythagorean theorem to solve for the missing side. 13 = hypotenuse, and 12 = a leg.  
$a^{2} +b^2=c^2$ 
Plug in values
$12^{2} +b^2=13^2$
subtract 12 squared from both sides
$b^2=13^2 -12^{2}$
$13^2 -12^{2} =25$
squared root of 25 is 5. the missing leg is 5 so sin is opp/hyp or 5/13