4.　初等幾何学の作図例題

10 REM   三角形の六点円（テーラー円）を求める"
20 DPERAS
30 DEF2PT P : DEF2ED E : DEF2CR C : DEF2LN L
40 LET PA,PB,PC=100,200,-200,-200,200,-200
50 E1=PB@PC : E2=PC@PA : E3=PA@PB
60 EN1=E1@PA : EN2=E2@PB : EN3=E3@PC
70 PD=EN1 : LET X,Y=PD: DPTEXT X,Y,"D"
80 PE=EN2 : LET X,Y=PE: DPTEXT X,Y,"E"
90 PF=EN3 : LET X,Y=PF: DPTEXT X,Y,"F"
100 E4=E3@PD : E5=E1@PE : E6=E2@PF
110 E7=E2@PD : E8=E3@PE : E9=E1@PF
120 LET X,Y=PA: DPTEXT X,Y,"A"
130 LET X,Y=PB: DPTEXT X,Y,"B"
140 LET X,Y=PC: DPTEXT X,Y,"C"
150 PG=E7 : LET X,Y=PG: DPTEXT X,Y,"G"
160 PH=E4 : LET X,Y=PH: DPTEXT X,Y,"H"
170 PK=E8 : LET X,Y=PK: DPTEXT X,Y,"K"
180 PL=E5 : LET X,Y=PL: DPTEXT X,Y,"L"
190 PM=E9 : LET X,Y=PM: DPTEXT X,Y,"M"
200 PN=E6 : LET X,Y=PN: DPTEXT X,Y,"N"
210 GROFF
220 L1=LBSEC(PL,PM) : L2=LBSEC(PM,PN) : P0=L1&L2
230 R0=DIS(P0,PM) : LET C0=P0,R0 : C0=C0
240 GRON
250 C0=C0
260 DPTEXT -100,200,"六点円"

図4.6　六点円