exm020312.m

matlab电子书籍

syms a r theta phi positive					
x=r*cos(theta);x=subs(x,r,a*theta);
y=r*sin(theta);y=subs(y,r,a*theta);
dLdth=sqrt(diff(x,theta)^2+diff(y,theta)^2);
L=simple(int(dLdth,theta,0,phi)) 

L_2pi=subs(L,[a,phi],sym('[1,2*pi]'))		
L_2pi_vpa=vpa(L_2pi)

L1=subs(L,a,sym('1'));
ezplot(L1*cos(phi),L1*sin(phi),[0,2*pi])	
grid on							
hold on							
x1=subs(x,a,sym('1'));			
y1=subs(y,a,sym('1'));
h1=ezplot(x1,y1,[0,2*pi]);	
set(h1,'Color','r','LineWidth',5)
title(' ')
legend('螺线长度-幅角曲线','阿基米德螺线')
hold off