Can someone find the circumference of the circle

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

Identify a1 and r for the geometric sequence an= -256(-1/4) n-1

Two variables, x and y, vary inversely, and x=12 when y=4. what is the value of y when x=3?