SOLUTION: Prove that : cos(72°) =(1/2)sqrt(4sin²(36)-1)
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Question 1191002: Prove that : cos(72°) =(1/2)sqrt(4sin²(36)-1)
Answer by MathLover1(20849) (Show Source): You can put this solution on YOUR website!
Prove that :
solve left side:
.....use identity °
use identity
........where ° and °
solve right side:
.....
=
=
=
=
so, both sides have same answer
then
->proven
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