Been scratching my head over this for a while now.  See attached screenshot.

I have a fully defined triangle in sketch 4 and I want each of those 3 lines to drive a line length in a separate sketch, in sketches 1, 2 and 3 respectively).

I can't seem to find a way to tell solidworks what I need to do.  When I select one line from each sketch I was expecing the "relation" options to become available, but no such options appear.

All the lines I'm inerested in are parallel to the top plane and are co-planar to each other in the drawing space.

Ultimately I want the triangle to have dimensions on two of it's lines and let the hypotenuse be driven by them and then the circular features of the solid body are recalculated automatically.  Red, green and blue line pairs all need to be different lengths, for instance red=red=50mm, green=green=40mm and blue=blue=30mm.

I do realise that I could jut put the dimension on the circle itself but I want to do it in a separate sketch to illustrate the "right-angled triangle" method of calculating pipe-joint diameters.

Is this even possible?