87/62 = 1 and 25/62 (simplest form)
They are to make variables.
I would interpret that the side of the cube is four since the volume of the cube is cube of the side. In this case 4 is the side and 4x4x4=64.
5x4=20 i think this is the right one
2cosx=2sin2x. Sin2x is an identity for 2sinxcos. So 2[2sinxcosx] gives you 4sinxcosx. 2cosx=4sinxcosx. Divide 2cosx on both sides and gives you 2sinx=0 and divide again, sinx=0. Sinx is 0 at 0 and 360 degrees, or pi and 2pi. So thats what x would be. 0,360,pi,2pi.
