PRINT
PRINT "＜はさみうち法＞"
PRINT "次の連立方程式の解の近似値を求めます。"
PRINT "    F(x)=x^2-1"
PRINT "    G(x)=x+1"
PRINT   
DEF F(x)=x^2-1
DEF G(x)=x+1
IF F(0)=G(0) THEN
   PRINT "(x,y)=(";0;",";F(0);")"
END IF
IF F(100)=G(100) THEN
   PRINT "(x,y)=(";100;",";F(100);")"
END IF
IF F(-100)=G(-100) THEN
   PRINT "(x,y)=(";-100;",";F(-100);")"
END IF
LET Xa=0
LET Xb=100
LET C=30
DO WHILE C>0
   IF (F(Xa)-G(Xa))*(F(Xb)-G(Xb))<0 THEN
      LET Xc=(Xb+Xa)/2
      IF (F(Xa)-G(Xa))*(F(Xc)-G(Xc))<0 THEN
         LET Xb=Xc
      ELSE
         LET Xa=Xc
      END IF
      LET C=C-1
   END IF
   PRINT "        ( ";Xa;",";Xb;")"
LOOP
IF Xa<>0 THEN
   PRINT " (x,y)≒( ";Xa;",";G(Xa);")"
   PRINT " (x,y)＝( ";ROUND(Xa,5);",";ROUND(G(Xa),5);")"
END IF
PRINT
LET Xa=-100
LET Xb=0
LET C=30
DO WHILE C>0
   IF (F(Xa)-G(Xa))*(F(Xb)-G(Xb))<0 THEN
      LET Xc=(Xb+Xa)/2
      IF (F(Xa)-G(Xa))*(F(Xc)-G(Xc))<0 THEN
         LET Xb=Xc
      ELSE
         LET Xa=Xc
      END IF
      LET C=C-1
   END IF
   PRINT "                ( ";Xa;",";Xb;")"
LOOP
IF Xa<>0 THEN
   PRINT "         (x,y)≒( ";Xa;",";G(Xa);")"
   PRINT "         (x,y)＝( ";ROUND(Xa,5);",";ROUND(G(Xa),5);")"
END IF   
PRINT
SET WINDOW -4,4,-4,4
DRAW GRID
FOR i=-4 TO 4 STEP 0.001
   PLOT LINES: i,F(i);
NEXT i
PLOT LINES
FOR i=-4 TO 4 STEP 0.001
   PLOT LINES: i,G(i);
NEXT i
END