要绘制摆线轮齿廓，程序如下： 
iH=30/29;
Orrp=0.3676; 
Orp=0.1981;
a=4.5;
zp=30;
rp=186;
rrp=12.2;
K11=a*zp/(rp+Orp);
x1=sym('(rp+Orp-(rrp+Orrp)*(1+K11^2-2*K11*cos(φ))^(-1/2))*cos((1-iH)*φ)-a*(rp+Orp-zp*(rrp+Orrp)*(1+K11^2-2*K11)^(-1/2)*cos(iH*φ)/(rp+Orp))');
y1=sym('(rp+Orp-(rrp+Orrp)*(1+K11^2-2*K11*cos(φ))^(-1/2))*sin((1-iH)*φ)+a*(rp+Orp-zp*(rrp+Orrp)*(1+K11^2-2*K11)^(-1/2)*sin(iH*φ)/(rp+Orp))');
ezplot(x1,y1)
运行后提示：
??? Error using ==> sym.sym>char2sym
Not a valid symbolic expression.

Error in ==> sym.sym at 92
   S = char2sym(x);