Author Topic: Advanced Trigonometry :)  (Read 7123 times)

MrPuzzle

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Advanced Trigonometry :)
« on: 七月 29, 2004, 09:47:05 am »
Prove

  cos π/7 - cos 2π/7 + cos 3π/7 = 1/2

without actually computing the values.

idiot94

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Advanced Trigonometry :)
« Reply #1 on: 七月 29, 2004, 04:00:15 pm »
Consider the roots of x^7 = 1, you immediately got the result.

Friends, I will be on my way to Alaska tomorrow morning! :) ... (that is why I was busy this week... to finish up the stuff at work before vacation.. ~_* )...

Hope I can bring some cool pics back for you guys :)
In general, the men of lower intelligence won out. Afraid of of their own shortcomings ... they boldly moved into action. Their enemies, ...  thought there was no need to take by action what they could win by their brains. Thucydides, History

MrPuzzle

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Advanced Trigonometry :)
« Reply #2 on: 七月 30, 2004, 09:06:32 am »
Yes, X^7=1 is the key.

Good job and have a wonderful vacation.