iOS How to calculate the length of a touch/finger drawn line

[Bayan]

I'm writing a code in which I ask the user to mark dots on a picture by touching the screen then I link each two to create a straight line..
What I want to do now is to calculate/measure the length of each line, is there a method to do that? or should I do it myself? if so, can someone give me a basic idea of how such method works?

Thanks in advance!

 

[robbieduncan]

Basic maths to find the distance between two points:

http://www.purplemath.com/modules/distform.htm

 

[Ides]

Distance

It's the pythagorean theorem:

 float distance = sqrtf( powf(x1-x2, 2) + powf(y1-y2, 2) );

where (x1, y1) and (x2, y2) are the two points that are connected.

Edit: Thanks for the tip, chown33

 

[chown33]

 float distance = sqrtf( powf(x1-x2, 2) + powf(y1-[COLOR="Red"]y1[/COLOR], 2) );

Bug.