I'm trying to make a triangle that has rounded corners. The triangle will look like this:

The bottom left corner is the only one that seems fairly easy to make, mostly because that is a 90 degree 'turn'. That turn is made using the Q command in SVG with the following parameters:
Q x,y + height, x, y + height - RADIUS starting at the right bit of the arc I'm creating.
However, the other corners are variable, depending on the triangle size. I can calculate their angles using atan() functions, but I have no clue how to implement them. I would like it to follow the RADIUS variable (5 in this case).
Any ideas?