画图求得弦长0.8616m
直径D=3.6米弧长C=0.87米弦长L是多少?弧半径为R,弧所对的圆心角为A。R=D/2=3.6/2=1.8米A=C/R=0.87/1.8=0.4833333弧度=0.483333333*180/π=27.593度L=2*R*SIN(A/2) =2*1.8*SIN(27.593/2) =0.8616米
3.6arcsin(x/3.6)=0.87x=(18*sin(29/120))/5=0.86155629177578