How to use fmincon for my function with 2 variables?

function [pointoftangency] = Tangentpoint(X,Y,amplitude)
ptf=amplitude*sin(2*pi*x./25)+((2*pi*amplitude/25)*cos(2*pi*x./25)*(X-x))-Y
end

and my constraint equation is

amplitude*sin(2*pi*x/25)=0;

How do I solve this using fmincon??

[Rik]

Have a read here and here. It will greatly improve your chances of getting an answer.

You can 'trick' fmincon by entering your variables as a vector into your function.

[Walter Roberson]

Which are the two variables? You have X, Y, and amplitude as inputs to Tangentpoint, and your code also uses x as well. Your code computs ptf, but your function expects pointoftangency to be output.

What is it that needs to be minimized?

Answer 1

[Walter Roberson]

Assuming that it is ptf that needs to be minimized with X, Y, amplitude constants, then the solution is that ptf becomes arbitrarily small (towards negative infinity) as x approaches positive infinity, assuming the value 2*Pi*amplitude*(X-50*Z)*(1/25)-Y when x = 50*Z with Z being an integer.

ptf becomes arbitrarily small (towards negative infinity) as x approaches negative infinity when x = 50*Z+25 with Z being an integer.