Math, asked by ShrutikaSansaria, 1 year ago

Prove that cos2π/7+cos4π/7+cos6π/7=-1/2

Answers

Answered by ishratmulani123

4

Cos 12py /7.
= cos ( 14py - 2py/ 7)
= cos ( 2py - 2py/ 7)
= cos (2 py/7)
= cos -120
= - 1/2.

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