%a
t=0:0.1:8*pi;
x=(e.^(-0.05)).*sin(t);
y=(e.^(-0.05*t)).*cos(t);
z=t;
subplot(2,2,1)
plot3(x,y,z,'color','r','LineWidth',2);
%b
t=0:0.1:2*pi;
x=2.*sin(3.*t).*cos(t);
y=2.*sin(3.*t).*sin(t);
z=sin(3.*t);
subplot(2,2,2)
plot3(x,y,z,'color','g','LineStyle','-','LineWidth',1);
%c
t=0:0.1:2*pi;
x=3.*cos(t)+cos(10.*t).*cos(t);
y=3.*sin(t)+cos(10.*t).*sin(t);
z=sin(10.*t);
subplot(2,2,3);
plot3(x,y,z,'color','b','LineWidth',4);
%d
t=0:0.1:8*pi;
x=5.*cos(t)-cos(5.*t);
y=5.*sin(t)-sin(5.*t);
z=t;
subplot(2,2,4)
plot3(x,y,z,'color','c','LineWidth',4)