(sina/2+cosa/2)^2+2sin^2(π/4-a/2)=
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(sina/2+cosa/2)^2+2sin^2(π/4-a/2)=
(sina/2+cosa/2)²+2sin²(π/4-a/2)
=sin²a/2+cos²a/2+2sina/2cosa/2+2sin²(π/4-a/2)
=1+sina+1-cos[2(π/4-a/2)]
=2+sina-cos(π/2-a)
=2+sina-sina
=2
=sin²a/2+cos²a/2+2sina/2cosa/2+2sin²(π/4-a/2)
=1+sina+1-cos[2(π/4-a/2)]
=2+sina-cos(π/2-a)
=2+sina-sina
=2
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