# Finding the intersection points between two curves

9 views (last 30 days)
raha ahmadi on 30 Jul 2021
Commented: Star Strider on 7 Aug 2021
I need to find the intersection points of this equation:
this is my code. I dont know what is the best way . Also when I plot in terms of I have some periods but when I plot in terms of β I have only one period. How I can plot it in terms of beta but with nulti perids?
h=20;
K=13.6;
l=1148e-6;
g1=fplot(@(beta)tan(beta*l));
hold on
g2=fplot(@(beta)2*h*beta*K/(K^2*beta^2-h^2));
Warning: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and shape as the input arguments.

Star Strider on 30 Jul 2021
Several options —
h=20;
K=13.6;
l=1148e-6;
f1 = @(beta)tan(beta*l);
f2 = @(beta)2*h*beta*K./(K^2*beta.^2-h^2);
figure
g1 = fplot(f1);
hold on
g2 = fplot(f2);
g3 = fplot(@(beta) f2(beta)-f1(beta), '--'); % Use 'fsolve' On 'g3' To Find The Intersections
Another option:
format long
Xint = interp1(g3.YData, g3.XData, 0)
Xint =
0
.
Star Strider on 7 Aug 2021
Thank you!
As always, my pleasure!
.

darova on 30 Jul 2021
I'd try fsolve for solving
fplot(f,[0 10])
raha ahmadi on 30 Jul 2021
Dear darova
Thank you for your help, I read fsolve but I think it solves a system of nonlinear equations. I used fzero instead but I only got one answer I need solve it in some periods and get more roots
Best regards

R2018b

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