Question

cos36°-cos 72 ° equal to​

Answer 1

cos36∘−cos72∘=−2sin54∘sin(−18∘)

[cosA−cosB=2sin(2D−C)(sin2C+D)]

cos36∘−cos72∘=2(45+1)×(45−1)

                              =42=21

hope this helps