A.2sinx+1=0

B.2cos^2x-1=0

C.3tan^3x-tanx=0

D.2sin^2x=2+cosx

I really need help.. I have my answers here but im not sure if they are correct:

A.x=7/6pi, 11/6pi

B.x=pi/4 7/4pi

C.x=pi/6 7/6pi 2pi pi

D.x=pi/2, 3/2pi pi/3 5/3pi

I also need these checked

Using a sum of difference identity find exact values for the following:

A.Cos75(degrees)

B.Sin15(degrees)

C.tan345(degrees)

I got

A.*squareroot*6-2/4

B.*squareroot*6-2/4

C.3-*squareroot*3/3

For problems 2 and 3 find the following.

A.cos(x-y): sin(x-y); tan (x-y); the quadrant (x-y) is in.

B.cos(x+y); sin(x+y) tan(x+y) the quadrant (x+y) is in.

2.If (pi/2)<x<pi and pi<y<(3pi/2) and cosx=-5/13 and tany=3/4

3.If pi<x< or equal too(3pi/2) and (3pi/2)<y<2pi, and secx=-41/9 and tany=-12/5

If you could show me how to do them it would be appreciated.