Creating A Class That Draws Triangles For A Project

I'm creating a javascript class that draws triangles for a project I'm working on (none of the other vector solutions for triangles were satisfactory so I'm writing my own).

Anyway here is a small snippet of code:

Code:

The idea of the code is to create a small div in the middle of the triangle that a user can click on, pretty basic stuff.

Problem with highlighted code is, on their own they work, together they dont.

IE, if I only set the LEFT of the div, it moves across the screen to required position.

If I only set the TOP of the div, it moves down the screen to the required position.

But BOTH together (as above) just make the div dissapear somewhere. Weird.