# diagonals

## Derivation / Proof of Ptolemy's Theorem for Cyclic Quadrilateral

Ptolemy's theorem for cyclic quadrilateral states that the product of the diagonals is equal to the sum of the products of opposite sides. From the figure below, Ptolemy's theorem can be written as

$d_1 d_2 = ac + bd$

- Read more about Derivation / Proof of Ptolemy's Theorem for Cyclic Quadrilateral
- Log in or register to post comments
- 6907 reads