how can I solve this problem..
显示 更早的评论
syms theta0
th = -y+cos(theta0)*x^2-g*x^2/(2*v0^2*sin(theta0)^2) == 0;
theta0 = [0 pi];
stheta0 = fzero(th,theta0);
I want to get two roots for theta0 but when I erased 'theta0 = [0 pi]' , it was too complicated.
回答（1 个）
Um, what do you expect?
syms theta0
x=90; g=9.81; v0=30; y0=1.8; y=1;
th = -y+tan(theta0)*x-g*x^2/(2*v0^2*cos(theta0)^2)+y0;
pretty(th)
Do you expect an analytical solution, something nice and simple and very pretty?
thsol = solve(th)
You should be able to effectively reduce this to effectively a 4th degree polynomial in terms of sin(theta0), so 4 roots.
vpa(thsol)
There are probably infinitely many solutions since trig functions are periodic. I don't see how much better than that you can rationally expect? Honestly, I'd say you are pretty lucky, in that solutions are easily generated\. Just pick the one that makes sense to you.
类别
在 帮助中心 和 File Exchange 中查找有关 Assumptions 的更多信息
2021-4-20
2021-4-21
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
