t=solve('32*sqrt(5)*(1-exp(-20*t*sqrt(5)))*exp(-20*t*sqrt(5))/(1+exp(-20*t*sqrt(5)))^3-390.625/(0.625*t+1)^3') t=double(t); A=t==real(t); tt=t(A)
附录3：clear clc
v=linspace(125,0,1000); a=(0.375*v.^2-750)/75; plot(v,a)
axis([0 125 0 70]) arrow([40 0],[130 0]) arrow([40 0],[40 70]) gtext('a-v曲线') gtext('v/m.s-1') gtext('a/m.s-2')
saveas(gcf,'jianmo3.jpg')
附录4：clc clear
v=solve('v^2-2000')
11
