Help with trig equations?

Feb 2010
9
0
I need help with doing these. Please show working out.
Sorry for the multiple questions. I don't know how to do them (Crying)

1) 2cos^2 2x + 3sin2x - 3

2) 3sec^2 3α - tan2α = 5

3) 3sin2θ + 2sinθ = 0

4) sin θ - cos (θ/2) = 0
 
Jun 2010
89
14
Iran
Hi. i am using my phone to answer you, so i cant write much. to solve the 1st, you should convert cosine into sine. then you have a quadratic equation.when solving that,you earn the four general solutions: x=k.pi-pi/12 , x=k.pi+7pi/12 , x=k.pi-pi/4 , x=k.pi+3pi/4. which just the 1st is true! to solve the others, you can use the linke in my signature... .