1. ## general solution

find the general solution of:

sin(2x+30)=cos3x

2. Originally Posted by rionariona
find the general solution of:

sin(2x+30)=cos3x
what have you tried. it sees to me that applying the addition formulas is the way to go.

3. Originally Posted by rionariona
find the general solution of:

sin(2x+30)=cos3x
The addition formula and then the double angle formulae.

Rewrite cos(3x) as cos(2x+x) if you have to derive it. If not google it

4. i tried google nd couldnt get anything

5. List of trigonometric identities - Wikipedia, the free encyclopedia

$\cos 3\theta = 4 \cos^3\theta - 3 \cos \theta$

6. how do i get the general solution with that?

7. Originally Posted by rionariona
how do i get the general solution with that?
$\sin (2x+30) = \sin (2x) \cos (30) + \cos (2x) \sin (30)$

$\cos (3x) = 4 \cos^3 (x) - 3 \cos (x)$

$\sin (2x) \cos (30) + \cos (2x) \sin (30) = 4 \cos^3 (x) - 3 \cos (x)$

If you need more help please show what working you've done. I'm not prepared to do this question for you

8. thank you so much for the help, this is the answer i have arrived at:

sin(2x+30)=cos3x
sin(2x+30)=sin(90-3x)
5x=60+360.k
x=12+72.k