A Diagonal Dot Identity

Problem

In quadrilateral ABCDABCD, the diagonals satisfy AC=aAC = a and BD=bBD = b. Find

(AB+DC)(BC+AD)\left(\overrightarrow{AB} + \overrightarrow{DC}\right)\cdot\left(\overrightarrow{BC} + \overrightarrow{AD}\right)

in terms of aa and bb.

Answer

Solution

Difficulty6/10
Topicsplane geometry, Polarization Identity, vectors

Whiteboard

Your sketch is saved only in this browser. To share it, export your drawing as an image (whiteboard menu → Export as → PNG), then upload that image in the comments below.

Discussion

Ask questions, share alternate solutions, and use LaTeX freely.

0 comments
Log in to join the discussion.

No comments yet.