unable to solve sybolically.

Question

jad kozah 2019-3-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/452100-unable-to-solve-sybolically

回答： jad kozah 2019-3-25

Untitled456464.m

在 MATLAB Online 中打开

I'm trying to solve this equation but the software keeps on giving me this warning : unable to solve sybolically.

And it goes to vpasolve giving me one solution for x and y while i expecting 6 solutions for x and 6 for y.

when i reduce my equation to

psi = 20.*((y.*cosd(-30))-(x.*sind(-30))) + (c.*log (sqrt((x-1).^2 + (y-1).^2))) + (c.*log (sqrt((x-3).^2 + (y-2).^2))) 

Matlab will solve it with no problem giving me two soltions for each x and y as expected.

Any help to solve the entire equation and get my 6 solutions for each x and y ?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Krishna Kumar 2019-3-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/452100-unable-to-solve-sybolically#answer_367159

Why do you declare this?- [x,y] = meshgrid(0:0.5:10, 0:0.5:10);

if you are anyway declaring x and y to be symbolic later. This could be a source of problem.

2 个评论
显示无隐藏无

jad kozah 2019-3-25

Thank you for your answer .

I tried to remove it .

i'm still getting the same error .

Any help ?

Krishna Kumar 2019-3-25

Probably the use of sol=solve(u,v); i.e. the syntax could be an issue. I understand this solves u=0 for the variable v. Is this what you want? or do you want to solve psi=0 for x and y?

请先登录，再进行评论。

Answer 2

jad kozah 2019-3-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/452100-unable-to-solve-sybolically#answer_367239

u is the derivative of psi with respect to y and v is the negative derivative of psi with respect to x.

so we will get u and v in function of x and y only.

u =

10*3^(1/2) + (1791925356007081*(2*y - 2))/(281474976710656*((x - 1)^2 + (y - 1)^2)) + (1791925356007081*(2*y - 4))/(281474976710656*((x - 3)^2 + (y - 2)^2)) + (1791925356007081*(2*y - 2))/(281474976710656*((x - 8)^2 + (y - 1)^2)) + (1791925356007081*(2*y - 4))/(281474976710656*((x - 6)^2 + (y - 2)^2)) + (1791925356007081*(2*y - 6))/(281474976710656*((x - 3)^2 + (y - 3)^2)) + (1791925356007081*(2*y - 6))/(281474976710656*((x - 6)^2 + (y - 3)^2))

v =

- (1791925356007081*(2*x - 2))/(281474976710656*((x - 1)^2 + (y - 1)^2)) - (1791925356007081*(2*x - 6))/(281474976710656*((x - 3)^2 + (y - 2)^2)) - (1791925356007081*(2*x - 6))/(281474976710656*((x - 3)^2 + (y - 3)^2)) - (1791925356007081*(2*x - 12))/(281474976710656*((x - 6)^2 + (y - 2)^2)) - (1791925356007081*(2*x - 12))/(281474976710656*((x - 6)^2 + (y - 3)^2)) - (1791925356007081*(2*x - 16))/(281474976710656*((x - 8)^2 + (y - 1)^2)) - 10

Then i want to get the unknows ( x and y )for u=0 and v=0

two equation ( u and v ) with two unknows ( x and y).

thank you in advanced