# Math Help - Theory questions using laws of trig

1. ## Theory questions using laws of trig

Hey all, I have a theory question using Trig Laws (and need to know if i'm right)

Q: To find the two possible values of cos(x) from a given value of sin(x) you would use??

my answ: The sum and difference of angles;
ie/ sin(A+B) = sinAcosB+cosAsinB
or sin(A-B)=sinAcosB-cosAsinB

is that right?

also- just to be sure- AAA (given three angles..) You can't find a side of a triangle right?

Thanks guys!!
-Brittany

2. Q: To find the two possible values of cos(x) from a given value of sin(x) you would use??

$\cos^2{x} = 1 - \sin^2{x}$

$\cos{x} = \pm \sqrt{1 - \sin^2{x}}$