1. Solve sin(4x)=cos(2x) for 0 degree to 180 degree. (Tips. there are 4 answers)
2. It is given that A,B.C are the interior angles of triangle ABC respectively, Also sin(A)^2 + sin(B)^2=1-cos(A+B)cos(A-B). Prove that sin(A)^2+sin(B)^2+sin(C)^2=2+2cos(A)cos(B)cos(C).