proof of parallelogram law

The proof supplied here for the parallelogram lawMathworldPlanetmathPlanetmath uses the properties of norms and inner productsMathworldPlanetmath. See the entries about these for more details regarding the following calculations.

x+y2+x-y2 =x+y,x+y+x-y,x-y

Title proof of parallelogram lawPlanetmathPlanetmath
Canonical name ProofOfParallelogramLaw1
Date of creation 2013-03-22 16:08:15
Last modified on 2013-03-22 16:08:15
Owner Wkbj79 (1863)
Last modified by Wkbj79 (1863)
Numerical id 6
Author Wkbj79 (1863)
Entry type Proof
Classification msc 46C05
Related topic ProofOfParallelogramLaw
Related topic AlternateProofOfParallelogramLaw