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Prove that: Cos2pi/7+cos4pi/7+cos8pi/7=-1/2

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Prove that: Cos2pi/7+cos4pi/7+cos8pi/7=-1/2

asked Jan 8, 2020 171k views

2 votes

Prove that: Cos2pi/7+cos4pi/7+cos8pi/7=-1/2

Mathematics
middle-school

Evan Shortiss asked

by Evan Shortiss

7.8k points

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1 Answer

1 vote

Answer:

1. use a calculator to help

2. that's wrong because it equals 1.333...

Trond Kristiansen answered Jan 14, 2020

by Trond Kristiansen

8.7k points

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