posted by Pam .
Using the Law of Cosines for vectors, give a vector proof that if quadrilateral ABCD is a rhombus, diagonal AC bisects <BAD. As part of your proof include a carefully drawn figure a statement of what is given, and a statement of what you are proving. I need help with this. I have no idea how to start or go about this.
a web search for "law of cosines for vectors" shows various articles. The 4th entry at tri-c dot edu ha a diagram and explanation.