How this calculation works
Recover a cyclic quadrilateral’s second diagonal from the first and its four sides.
THE FORMULA
AC × BD = AB × CD + BC × DAA worked example
A 3 by 4 rectangle gives BD=(9+16)/5=5.
Good to know
The side and diagonal data must describe a convex cyclic quadrilateral.
Reference: OpenStax Algebra and Trigonometry, Trigonometric Applications (opens in a new tab) ↗
Read the result
Recover a cyclic quadrilateral’s second diagonal from the first and its four sides.
The primary result is labeled “Diagonal BD”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
The side and diagonal data must describe a convex cyclic quadrilateral.
For a related exercise, try the circle calculator.
A few questions, answered
How can I check the default inputs by hand?
A 3 by 4 rectangle gives BD=(9+16)/5=5.
Which rule does this calculator apply?
AC × BD = AB × CD + BC × DA