2.5
习题三 3.1
clf,clc,clear
t=(0:18/100:18)'; xi=0.2:0.2:0.8;
beita=sqrt(1-xi.^2); sita=atan(beita./xi);
y=1-exp(-t*xi).*sin(t*beita+ones(101,1)*sita)./(ones(101,1)*beita); figure(1)
plot(t,y(:,1),'b:',t,y(:,2),'r-.',t,y(:,3),'g-',t,y(:,4),'ko')
legend('\\xi=0.2','\\xi=0.4','\\xi=0.6','\\xi=0.8')
1.61.4?=0.2?=0.4?=0.6?=0.81.210.80.60.40.20024681012141618
3.2
clf,clear x=-50:1:50; y=-40:1:60;
z=1./(sqrt((1-x).^2+y.^2)+sqrt((1+x).^2+y.^2)); figure(1)
plot3(x,y,z),box on [X,Y]=meshgrid(x,y);
Z=1./(sqrt((1-X).^2+Y.^2)+sqrt((1+X).^2+Y.^2)); figure(2) mesh(X,Y,Z) figure(3) surf(Z)
0.080.060.040.020100500-50-50050
0.50.40.30.20.10100500-50-50050
