Bretschneider's Formula
Given a general Quadrilateral with sides of lengths 
, 
, 
, and 
(Beyer 1987), the Area is given by
where
and 
are the diagonal lengths.See also Brahmagupta's Formula, Heron's Formula
References
Beyer, W. H. (Ed.). CRC Standard Mathematical Tables, 28th ed. Boca Raton, FL: CRC Press, p. 123, 1987.
- Rotation Group
- Rotation Matrix
- Rotation Number
- Rotation Operator
- Roth's Removal Rule
- Roth's Theorem
- Rotkiewicz Theorem
- Rotoinversion
- Rotor
- Rotunda
- Rouché's Theorem
- Roulette
- Round
- Rounding
- Routh-Hurwitz Theorem
- Routh's Theorem
- RSA Encryption
- RSA Number
- Rubber-Sheet Geometry
- Rubik's Clock
- Rubik's Cube
- Rudin-Shapiro Sequence
- Rudvalis Group
- Rule
- Ruled Surface