x=-7:0.01:7;
f1=atan(x+2).^2;
f2=atan(x-2).^2;
plot(x,f1,x,f2)
plot(x,f1,x,f2,x,0.5*f1+0.5*f2)
hold
plot(x,0.9*f1+0.1*f2,'m')
plot(x,0.1*f1+0.9*f2,'y')
plot(x,0.7*f1+0.3*f2,'g')
plot(x,0.3*f1+0.7*f2,'k')

