SOLUTION: cos^2 π/8 + cos^2 3π/8 +cos^2 5π/8 + cos^2 7π/8

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Question 1075809: cos^2 π/8 + cos^2 3π/8 +cos^2 5π/8 + cos^2 7π/8
Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
.
1.   cos%28pi%2F8%29  = -cos%287pi%2F8%29.    Obviously.

     cos%283pi%2F8%29 = -cos%285pi%2F8%29.    Obviously.


2.   cos%28pi%2F8%29 = sqrt%282%2Bsqrt%282%29%29%2F2.

     See the lesson  Trigonometric functions of half argument - Examples  in this site.


3.   cos%283pi%2F8%29 = sin%28pi%2F8%29    ( Obviouly )

                        = sqrt%282-sqrt%282%29%29%2F2

     See the lesson  Trigonometric functions of half argument - Examples  in this site.


4.   Now you are armed / prepared to complete this assignment on your own.