Verify: sin(Θ/3)cos(Θ/3) = 1/2sin(2Θ/3)

Ihonestly don’t understand this at all

Which shows one way to determine the factors of  x3  +  5x2  –  6x  –  30 by grouping? x(x2  –  5)  +  6(x2  –  5)x(x2  +  5)  –  6(x2  +  5)x2(x  –  5)  +  6(x  –  5)x2(x  +  5)  –  6(x  +  5)

Volume of a cylinder with a radius of 13 in and height of 30 in