Show that if x and y are vectors in R2, then x+y and x-y are the two diagonals of the parallelogram whose sides are x and y.
This is a question for my homework. Is there some kind of formal proof I need to provide?
i don't know if this would be acceptable but try drawing the vectors x and y
and then connect the lines for x+y and x-y , but i'm not sure if this diagram would be acceptable for the proof
and take a look at this and see if it helps:
Parallelogram law - Wikipedia, the free encyclopedia