
Re: intersection of a surface with a plane
Posted:
Jan 16, 2013 7:20 AM


> Thank you very much for your reply. > > I tried plotting. I got the plots. But I don't how to > spot the location(coordinates) of the intersection. > > > syms a b > lhs='2*cos(a)*cosh(b)(b/aa/b)*sin(a)*sinh(b)2'; > rhs='0'; > > [a]=solve(lhs,a,b); > > figure > ezsurf(lhs,[5,5,5,5]) > hold on > ezsurf(rhs,[5,5,5,5]) > > . > My main aim was to find the roots of the equation. > So, I plotted the equations, from which I can find > the roots. > > zdiff = lhs  rhs; > C = contours(lhs, rhs, zdiff, [0 0]); > % Extract the x and ylocations from the contour > matrix C. > aL = C(1, 2:end); > bL = C(2, 2:end); > > % Interpolate on the first surface to find > zlocations for the intersection > % line. > zL = interp2(a, b, lhs, aL, bL); > > % Visualize the line. > line(aL, bL, zL, 'Color', 'k', 'LineWidth', 3); > > Since, I could not able to spot the value of 'a' and > 'b', i was unable to find the roots of the eqn or the > intersection of the curves. > Problem with this : [a]=solve(lhs,a,b); was unable to > find the explicit solution. > > Thank you very much, > Murthy
What do you mean by "My main aim was to find the roots of the equation." ? You have one equation with two unknowns. Thus there are infinitely many "roots". The only thing you can do is to solve for a (dependent on b) or b (dependent on a). Example: a^2+b^21 = 0 Solve for a: a=+/ sqrt(1b^2) Solve for b: b=+/ sqrt(1a^2). Is it that what you try ?
Then test whether
smys a b solve(2*cos(a)*cosh(b)(b/aa/b)*sin(a)*sinh(b)2==0,a); or solve(2*cos(a)*cosh(b)(b/aa/b)*sin(a)*sinh(b)2==0,b);
works.
Best wishes Torsten.

