Explicit solution could not be found

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Yunho Choi
Yunho Choi 2011-8-19
i am students and i am learning matlab
but i got obstacle
please help me
this is my code
a=180;
b=220;
c=180;
syms pa;
syms be;
[pa,be]=solve('(cos(pa))^2+R1*(sin(pa))^2-(c/b)*((cos(be))^2+R1*(sin(be))^2)=0','(R1-1)*con(pa)*sin(pa)-a/b*((cos(be))^2+R1*(sin(be))^2)=0','(1+R1)*cos(pa)*sin(pa)+(1-R1)*cos(be)*sin(be)=0','pa','be');
(i'm sorry that equation make you feel dizzy.)
if i command this code
i get Explicit solution could not be found
what means of that message? how to solve it?
thank you very much for reading

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采纳的回答

Walter Roberson
Walter Roberson 2011-8-19
  1. If you have N equations in N variables, then asking to solve for fewer than N variables will almost always tell you that no solution could be found.
  2. In your second expression you need to fix the con(pa) to cos(pa)
  3. What are you going to do with the large number of solutions over the imaginaries?
  4. What are you going to do about the fact that sub-solutions to this problem involve polynomials which to any fixed numeric precision evaluate as having imaginary roots, but in the infinite precision limit the roots are completely real?

更多回答（1 个）

Friedrich
Friedrich 2011-8-19
Hi,
this can mean
  1. It's to complex for beeing solved symbolically
  2. Since you have 3 equations and 2 variables it can mean that no solution exists at all, e.g.
[x,y] = solve('x+y = 4','2*x+2*y = 8','x+y = 0')

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