Help please please please I’m tired :,)

Which sum or difference identity would you use to verify that cos (180° - ∅) = -cos ∅? a. sin (α -β) = sin α cos β – cos α sin β b. cos (α -β) = cos α cos β – sin α sin β c. cos (α -β) = cos α cos β + sin α sin β d. sin (α + β) = sin α cos β + cos α sin β

What are the soultion(s) to the quadratic equation 40- x^2=0

Me i’m stuck on all these questions besides the two bottom ones