Help simplifying?

Question

simplify.

 

2sin²x/2 -1

Answer 1

2sin²(x/2) - 1 = 2(±√[(1-cosx)/2])² - 1

 

                     = 2(1-cosx)/2 - 1

 

                      = 1 - cosx - 1 = -cosx

Answer 2

Assuming you mean:

 

2* (sinx*sins)/2 - 1

 

 

the 2 cancels  leaving

 

sin^2 - 1

 

which is sin^2 - (sin^2 + cos^2)  by trig identity

 

            = -cos^2