Which property is used in the last step to find that mc017-2.jpg?

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

Find the distance between the point (-3,-4), and (see the picture below)

A+b= 17, ab=70, find the value of |a-b|