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Find the value of cos^2pi/(16)+cos^2(3pi...

Find the value of `cos^2pi/(16)+cos^2(3pi)/(16)+cos^2(5pi)/(16)+cos^2(7pi)/(16)dot`

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`=cos^2pi/16+cos^2 3/16pi+cos^2 5/16pi+cos^2 7/16pi`
`=(1+cos(pi/8))/2+(1+cos(3/8pi))/2+(1+cos(5/8pi))/2+(1+cos(7/8pi))/2`
`=2+cospi/8+cos3/8pi+cos(pi-3/8pi)+cos(pi-pi/8)`
`=2+cospi/8+cos3/8pi-cospi/8`
`=2`.
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