# Point of a Parallelogram

• Delber

## Homework Statement

Given a parallelogram ABCD has vertices A(-1,2,-1), B(2,-1,3) and D(-3,1-3). Find the coordinates of C.

## The Attempt at a Solution

I'm extremely confused here. I do not know how to tell which coordinate is for which vertex on the parallelogram. I know this has to do with vector addition, but I can't picture it to solve the problem.

I believe that the convention is that A -> B -> C -> D -> A will traverse the parallelogram. So C is connected by lines to point D and point B. Hopefully that helps

A, B, C are three points in R^3. Imagine there are three points in your room or wherever. They can be connected to form a triangle. Think about how to turn a triangle into a parallelogram. You can get like three different parallelograms, but the question specifies that the parallelogram is ABCD, not ABDC or ACBD. What this means is described by CrazyIvan.

Opposite sides in a parallelogram are parallel and equal in length. So A - B = D - C.