I wish to create a sketch composed of arcs and lines that has built in relationships that will cause it to behave like a simplified version of the cross section of a flexible diaphragm.  For example.

<p><img data-media-type="picture" data-position="center" data-size="large" src=https://3dswym.3dexperience.3ds.com/media?id=0Ar0aKtNSP-hMRnAGg7kSw&v=aa8272c74a21ae6f1c8dd7a2aeea14b4ddc230727e9bcd30ed76e819302a1d2e data-media-id="0Ar0aKtNSP-hMRnAGg7kSw" style="width: 740px; height: 370px;"><img data-media-type="picture" data-position="center" data-size="large" src=https://3dswym.3dexperience.3ds.com/media?id=sP8_hjddQ1eQG4naIw6uQQ&v=be699d5a030f690e883eaa9aad26ec6218622da1408a83264664c75928b64a65 data-media-id="sP8_hjddQ1eQG4naIw6uQQ" style="width: 740px; height: 370px;"></p>

The way that I did this in the above sketch is to define the left hand vertical leg as a fixed dimension, and then make the right hand vertical leg length a quanity minus the left leg length (30 in this example).  I have tried several methods, and although I can make this work in a static situation, it is quite clunky.  What I really want to be able to do is to make this work inherently, like the fluidity of a tangent relationship.  Ideally I would simply be able to make the length of the combined line equal to a constant. 

Any ideas?