Question

How do I solve this?
polygons

Answer 1

I'm sorry, I forgot how to do this ):

Answer 2

I haven't a firm proof of this yet - but I think that this diagram does not have enough information to solve it.

ALL you know about the inner shape is that the diagonals are at right angles - it doesn't tell you anything about the orientation of the inner shape within the outer/ Although the drawing looks like the horizontal line is parallel to AB and CD you should not assume this so

this diagram ALSO fulfils the information you are given:



it seems likely to me that the shaded area in MY diagram is different from that in yours - so the diagram has more than 1 solution - i.e. it cannot be solved.