I compared the equation to sin^2(x) to sin(x) and I noticed a vast difference. The graphs below provide more insight:

sin^2(x) and sin(x)

I understand that two maximums on the sin(x) graphs (positive side) mean that one full rotation of the circle occurred, with the domain for now being 180 degrees orpi.

However, I cannot grasp why sin^2(x) does not contain a minimum below zero... can someone explain this to me?