■ピザの公平な分け方(その8)

  a=1/2・∫(0,π/4)r^2dθ

  b=1/2・∫(π/4,π/2)r^2dθ

  c=1/2・∫(π/2,3π/4)r^2dθ

  d=1/2・∫(3π/4,π)r^2dθ

  e=1/2・∫(π,5π/4)r^2dθ

  f=1/2・∫(5π/4,3π/2)r^2dθ

  g=1/2・∫(3π/2,7π/4)r^2dθ

  h=1/2・∫(7π/4,2π)r^2dθ

定数部分は除いてもよい.

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[1]2∫cos2(θ-α)dθ=sin2(θ-α)

a=cos2α+sin2α

b=sin2α-cos2α

c=-cos2α-sin2α

d=-sin2α+cos2α

e=cos2α+sin2α

f=sin2α-cos2α

g=-cos2α-sin2α

h=-sin2α+cos2α

  a+c+e+g=b+d+f+hが成り立つ.

  a+c=0,e+g=0,b+d=0,f+h=0

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