Calculating Line Length

[yellowhamster]

I'm writing a C program and I don't know how to measure the distance between two points. It's obviously pretty easy if they are along the x axis or y axis but what about at any arbitrary angle?

Thanks in advance for your help guys.

[soku11]

The formula is something like this:

d=Sqrt[(x_a-x_b)^2+(y_a-y_b)^2]

Its coming from the pythagoras theory Is it what you wanted??

[mholt]

Programmatically:

#include <math.h>
// point A(x1, y1)
// point B(x2, y2)

double distance = sqrt((x2-x1)^2 + (y2-y1)^2);

This works for any point anywhere on the X-Y coordinate plane.

[Xav]

This brings us back to the discussion of how maths is vital to programming. Yes, if you work out the triangle using Pythagoras, you can calculate the length. Just make sure the program runs the calculations in the order you want it to, though - remember, the exponentiation will be performed before the addition.

[dcs]

^ does not do exponentiation in C, it does an XOR.

#include <stdio.h>
#include <math.h>

double distance(double x1, double y1, double x2, double y2)
{
   return sqrt(pow(x2-x1,2) + pow(y2-y1,2));
}


int main(void)
{
   double dist = distance(0,0,3,4);
   printf("dist = %g\n", dist);
   return 0;
}

/* my output
dist = 5
*/

[mholt]

Oops. That you are right. Eh, I just got out of my computer science class (Java) - wrong mindset.

Thanks for the correction.

[Xav]

The math.h file ensures you can use the pow() function. It might be worth looking around the DOM in case there are any preset functions in cases like these.