Thread: some trig functions

i have some questions i really need help with

sin3 A = 3sin A - 4sin^3 A
(Hint use sin3 A = sin(2a + a)

and

sin3 x / sin x - cos3 x / cos x = 2

please help im stuck

Originally Posted by dave30001

i have some questions i really need help with

sin3 A = 3sin A - 4sin^3 A
(Hint use sin3 A = sin(2a + a)

um, use the hint! did you try? what did you get?

and

sin3 x / sin x - cos3 x / cos x = 2

please help im stuck

I will start you off:

Consider the LHS:







now can you finish up?