pythagorean theorem to find distance between two points

I am trying to limit the length of an old fashioned Qix video game so that the ball only travels within certain decreased parameters, rather than the full arena, when a specific command is entered in the command line. The full arena is 500, so I was trying to make the decreased arena be 400. I think that I need to use the pythagorean theorem to find the distance between x1 and y1, as well as x2 and y2, and then take that hypotenuse value and decrease it by a particular quantity. I have no idea how to make this happen, and have tried so many things that all result in errors. Please help!

Answer 1

[madhan ravi]

Read about hypot()

[jat]

I did, and I tried putting it in like that (C = sqrt(abs(A).^2 + abs(B).^2)) but it gives me an error. I also don't know how to shorten the hypotenuse after finding it, which is not included in the hypot() information.

[Walter Roberson]

What error did you encounter?

[jat]

it just says error in line C = sqrt(abs(A).^2 + abs(B).^2). It doesn't further specify.

[madhan ravi]

so see sir Walter's answer below

[Walter Roberson]

At the moment we do not know that you have defined A and B or what you defined them as and how they relate to x1, x2, y1, y2 .

[madhan ravi]

size(x1) size(x2) size(y1) size(y1) size(A) size(B) ?

Answer 2

[Walter Roberson]

[theta, r] = pol2cart(x2-x1, y2-y1);
[newrelx, newrely] = cart2pol(theta, r * reduction_factor);
new_x2 = x1 + newrelx; new_y2 = y1 + newrely;

[Walter Roberson]

By the way, this can be programmed more directly:

new_x2 = x1 + (x2 - x1) * reduction_factor;
new_y2 = y1 + (y2 - y1) * reduction_factor;