Solving 3D Vector equations
11 views (last 30 days)
Show older comments
I need to solve 3D vector equations having known and unknown position vectors. Equations have dot products, cross products, modulus and a combination of them.
Here's a one set of equations.
(l-o) x (q-o) . (c-o) = 0
o-q * [ (l-q).(q-c) ] = l-q * [ (o-q).(q-c) ]
Here, l,o,q,c are position vectors and l,o are known.
Thank you.
0 Comments
Accepted Answer
Andrew Newell
on 30 May 2011
Interesting equations. The first says that the points l,o,q,c are coplanar, but I'm not sure what the second means.
You can solve a system like this using fsolve. Since fsolve requires a function f(x) with vector x, you first need to combine your unknowns in a vector, e.g., x = [q; c]. Note: I am assuming your vectors are all column vectors.
Create a function
function y = myfun(x,l,o)
q = x(1:3); c = x(4:6);
y = [dot(cross(l-o,q-o),c-o)
abs(o-q)*dot(l-q,q-c) - abs(l-q)*dot(o-q,q-c)];
To solve your system of equations, you need to find an x that makes y equal to zero. Save this function in a file.
f = @(x) myfun(x,l,o);
Then make an initial guess for your solution, e.g., q0 and c0. Finally, solve:
x0 = [q0; c0];
xsol = fsolve(f,x0);
0 Comments
More Answers (1)
Jan
on 28 May 2011
Yes. If the equation can be solved, it can be solved in Matlab also.
If you want a more detailed answer, post the equation.
See Also
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!