Ask HN: Tool to query schema from drawings?

Looking for the best (preferably FOSS) tool for querying measurements on abstract geometric figures based on limited provided information. Preferably, this would support symbolic data representations (X = sin(Y)-cos(Z)).

Basically a tool to auto-complete high-school geometry problems. Looking for in in the context of rough woodworking/carpentry. I'm aware of the usual high-end CAD tools that would do this, I want something that is ultra-lightweight, for a quick "hand-sketch to finished product" development cycle.