What is the radius of a circle with a circumference of 15 cm

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

Evaluate-27 ^4/3/8 a) - 81/16 b) 81/16 c) 16/81

Lola says these two expressions have the same value. expression a expression b which explains whether lola is correct?