円と曲線の交点 #3
導関数を与えて微分係数を算出する方法。
PROGRAM INTERS IMPLICIT NONE DOUBLE PRECISION Y,YD,Y1,Y2,X,XN,E,X0 PARAMETER(E=1.0D-12,X0=0.9) Y1(X)=X*TAN(X) Y2(X)=SQRT(1-X**2) Y(X)=Y1(X)-Y2(X) YD(X)=(TAN(X)+X/COS(X)**2)-(-X/Y2(X)) X=X0 DO XN=X-Y(X)/YD(X) IF(ABS(Y(XN)).LT.E)THEN WRITE(UNIT=*,FMT=*)'X=',XN WRITE(UNIT=*,FMT=*)'X*TAN(X)=',Y1(XN) WRITE(UNIT=*,FMT=*)'SQRT(1-X**2)=',Y2(XN) STOP END IF X=XN END DO END C INTERSECTION POINT = (0.739085133,0.673612029)