# Starting the Sander's Parallelogram Proof

Can anyone help me set this problem up?

I am trying to figure out how to Prove the Sander's Parallelogram.

See it here:
http://www.tigel.nl/fun/files/opticals/Ill...ith_line-25.htm [Broken]

basically it is proving that the bisectors are of equal length

The question is: what would be needed to be established first in order to properly put together a proof? Are they a specific size? is there a relationship between the length of the two top sides? Any help would be great.

I don't need the proof - I am certain I can figure it out, but I would like a leg up on figuring out what would need to be established before starting to work it out.

many thanks!

Last edited by a moderator:
• JamesMaths

I think I should clarify what I am trying to do. I do not wish to construct the parallelogram. I want to be able to set up the initial conditions by which I could then ask someone to prove that the two bisectors are equal. By this I mean a standard two column mathematical proof.

I do know, after playing around that, as you can see from the image below, that AB is twice as big as BC. but beyond that, what else would one need to know?

many thanks with the help so far. pbuk