Math Is Fun Forum

Honore

Member

Registered: 2005-12-14

Posts: 1

Trigonometry

Hello,

Since I could not solve the following equation though applying all information I have about trigonometry, I would very appreciate if anybody could help or make some suggestion. Thanks for your time.

cos(2pi/11)+cos(4pi/11)+cos(6pi/11)+cos(8pi/11)+cos(10pi/11)=?

(Answer: -1/2)

ryos

Member

Registered: 2005-08-04

Posts: 394

Re: Trigonometry

Those angles be not on the unit circle, matey. Aaargh!

Ahem. I don't think they have coterminal angles on the unit circle, either.

Which means...use a calculator! Right? Don't tell me there's a goofy trig identity that will come to the rescue. I hates trig identities.

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El que pega primero pega dos veces.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Trigonometry

I didn't know it be talk like a pirate day. Yarr!

That scurvy dog, ryos, be correct. There be no identity that will rescue ye, landlubber.

At least, none that me or my parrot know. Arr!

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Why did the vector cross the road?
It wanted to be normal.

Chaotic Neutral

Member

Registered: 2005-10-31

Posts: 55

Re: Trigonometry

Aye aye, captain Rottingham! Calculators at deck, rrreform in rradials if ye think it will make ye life easier.

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As at night, we realise we will never Know and further thinking is pointless....Yet we start again and again

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Trigonometry

Me only contribution, mateys, is this ere lubberly sketch-ning

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman