Distance problem

I think there may be a simple solution to this, either something in C2 or a trigonometry answer (I think one of the basic trig rules covers this but can't remember it).

I have two points that I wish to know the distance between, but all I know is their start location (the centre of the screen), their angle and their distance from that point. Since I want my screen to be stretched, I can't used C2's built-in distance function.

So I guess if I know one corner of a triangle and the length and angle of the two sides coming from that point, is it possible to work out the distance between the two other points?

There is, and you don't need any trig for it. This will tell you the distance in pixels:

distance(sprite1.x, sprite1.y, sprite2.x, sprite2.y)

scirra.com/manual/126/system-expressions

It probably sounded like I know the locations of my sprites, but I don't. I'm placing them by moving them both a certain distance from the same location, but the screen can be stretched so I need to know the distance between them regardless of screen size.

So basically I know the point of a triangle, and the 2 angles and sides coming from that point. I'm trying to then calculate the length of the third side.