PRINT
PRINT "  双曲線 x^2−y^2 ＝ 1 ( x ≧ 1 ) のグラフを"
PRINT "反時計回りに 45°回転させます。"
PRINT
PRINT "すると、y ＝ (1/2)/x ( x ＞ 0 ) の反比例のグラフになります。"
PRINT
DEF X(t)=t*COS(PI/4)-(t^2-1)^(1/2)*SIN(PI/4)
DEF Y(t)=t*SIN(PI/4)+(t^2-1)^(1/2)*COS(PI/4)
DEF XX(t)=t*COS(PI/4)+(t^2-1)^(1/2)*SIN(PI/4)
DEF YY(t)=t*SIN(PI/4)-(t^2-1)^(1/2)*COS(PI/4)
SET WINDOW -0.5,4,-0.5,4
DRAW grid
FOR i=1 TO 4
   PLOT LINES: -1,i;4,i
   PLOT LINES: i,-1;i,4
NEXT i
SET LINE width 2
PLOT LINES: -1,0;4,0
PLOT LINES: 0,-1;0,4
SET LINE width 3
SET LINE COLOR 2
FOR t=1 TO 11.8 STEP 0.01
   PLOT LINES: X(t),Y(t);
NEXT t
PLOT LINES
FOR t=1 TO 11.8 STEP 0.01
   PLOT LINES: XX(t),YY(t);
NEXT T
END