You're expected to know the necessary identities:
If and , find and
 Since , we have a 3-4-5 right triangle. . Hence: .
Need some urgent help solving double argument properties for Calc/Trig course. Anybody out there that can help?
If cos A=3/5 and 0<A<90, find sin 2A and cos 1/2 A
Any help on this?