We had that problem on a geometry test in 9th grade, I will try digging it up and show you how ...if I can find it of courseforevergone said:I need some help trying to prove that if the diagonals of a quadrilateral bisect each other, the quadrilateral is a parallelogram.
I've been attacking this problem for hours but its no good :\.
I need to do this through vector proofs, though. If I could use congruent triangles, I would've been long done this problem :).Diane_ said:One way to do this is to show that you have a pair of congruent triangles. (There are actually several pair, but you only need one.) Remember the definition of a parallelogram - that'll give you the angles. There's one more property of parallelograms that will give you the sides that you need.