SOLUTION: Verify the identity (cos t+cos4t+cos7t) / (sin t+sin4t+sin7t)=cot4t

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Question 371826: Verify the identity (cos t+cos4t+cos7t) / (sin t+sin4t+sin7t)=cot4t
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
cos t+cos4t+cos7t = -2cos4tcos3t + cos4t = cos4t(1-2cos3t), by using -2cos%28%28A%2BB%29%2F2%29cos%28%28A-B%29%2F2%29+=+cosA+%2B+cosB.
Similarly,
sin t+sin4t+sin7t = -2sin4tcos3t + sin4t = sin4t(1-2cos3t), using 2sin%28%28A%2BB%29%2F2%29cos%28%28A-B%29%2F2%29+=+sinA+%2B+sinB. Therefore
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