# Math Help - Help with Math problems (Thanks!)

1. ## Help with Math problems (Thanks!)

I have 7 problems that I need help with. If you know just one, it would be EXTREMELY helpful!

1. Find all solutions to csc x= -1.15 in the interval 0<x<2pi.

2. Solve 15cos^2(x) - 7cosx-4=0 by factoring and find solutions in 0<x<2pi.

3. Use appropriate addition formula to simplify cos(A-B) given sec(A) = -2/√3 where 90°<A<180° and tan(B) = 1/4 where 0°<B<90°

4. Find all solutions of 2sin^2(x) - 9sin(x)+4=0. Express in radians

5. Find all solutions to sin(3x) = -√2/(2) in interval 0<x<2pi.

6. Find all solutions for 2sin(x) = √2cos(2x) in interval 0<x<2pi.

7. Verify the following identity: cos(4x) = 8cos^4(x) - 8cos^2(x) + 1.

Thank you!

2. 7 $cos(2(2x))=cos(2x)^2-sin(2x)^2$...and using double angle formulas again you get that $cos(2(2x))=[cos(x)^2-sin(x)^2]^2-[2sin(x)cos(x)]^2$..you can take it from there