■n角形のn等分(その9)

【1】面心五角形

  P0+P2=x1P1

  P1+P3=x2P2

  P2+P4=x3P3

  P3+P0=x4P4

  P4+P1=x5P0

(x1,x2,x3,x4,x5)=(t,0,1−t,1,1)

P0(1,0),P1(1,1)とおくと,

  P0+P2=tP1

  P1+P3=O

  P2+P4=(1−t)P3

  P3+P0=P4

  P4+P1=P0

P3=−P1=(−1,−1)・・・固定

P4=P0−P1=(0,−1)・・・固定

P2=tP1−P0=(t−1,t)・・・y=x+1上にある

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【2】面心六角形

  P0+P2=x1P1

  P1+P3=x2P2

  P2+P4=x3P3

  P3+P5=x4P4

  P4+P0=x5P5

  P5+P1=x6P0

(x1,x2,x3,x4,x5,x6)=(2/(s+t),s,0,t,2/(s+t),(s+t))

P0(1,0),P1(−1,1)とおく.

さらにt=−s−2とおくと,

  P0+P2=−P1

  P1+P3=sP2

  P2+P4=O

  P3+P5=(−s−t)P4

  P4+P0=−P5

  P5+P1=−2P0

P2=−P0−P1=(0,−1)・・・固定

P3=−P1+sP2=(1,−s−1)・・・x=1

P4=ーP2=(0,1)・・・固定

P5=−P3+(−s−2)P4=(−1,−1)・・・固定

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【3】面心七角形

  P0+P2=x1P1

  P1+P3=x2P2

  P2+P4=x3P3

  P3+P5=x4P4

  P4+P6=x5P5

  P5+P0=x6P6

  P6+P1=x6P0

(x1,x2,x3,x4,x5,x6)=(s,0,−1−s,t,0,−1−t,−1)

P0(1,0),P1(0,1)とおく.→各自

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