# Van Aubel's theorem

This theorem can be stated:

Start with any planar quadrilateral. Draw squares outwards from each edge, and draw lines between the centres of opposite squares. The two lines thus drawn will be equal in length, and perpendicular.

Here are some cheap nba jerseys illustrations (from answers.com):

As you see, mathematics one of the pleasant things about this theorem is its generality: the quadrilateral does not have to be convex; its edges may in cross, and one or two of wholesale nba jerseys them can even have zero length. cheap mlb jerseys I like this theorem: it has a nice method unexpectedness about it (to me, anyway); cheap mlb jerseys also it’s not hard to prove. I have a rather wholesale jerseys uninspiring proof using vectors. I Dollars? think this would make a nice student project: Zepheira verifying the theorem for different quadrilaterals, and (for the better students) proving Celebrate it.

There’s a lovely interactive diagram of this theorem at http://www.mste.uiuc.edu/dildine/geometry/vanaubel.html.