Thread: how do I do this trig addition formula problem?

Angle A is acute.
I have a list of trig formulas

here is the problem...
19. If sin A = 5/13, find sin 2A and cos 2A

Originally Posted by RaphaelB30

Angle A is acute.
I have a list of trig formulas

here is the problem...
19. If sin A = 5/13, find sin 2A and cos 2A

... use a reference triangle or the Pythagorean identity to find

Originally Posted by RaphaelB30

Angle A is acute.
I have a list of trig formulas

here is the problem...
19. If sin A = 5/13, find sin 2A and cos 2A

sin(x) = opp/hyp so you construct a right angled triangle with the opposite 5 and hypotenuse 13. You can then find the adjacent side easily enough and thus find cos(x).

For sin(2A) and cos(2A) use an identity