User:Michael Hardy/Hadley

In plane geometry, Hadley's theorem, asserted by Norman Wildberger to have been proved by Frank Hadley in 1980, states that in a triangle with an obtuse angle at B, in which in which the acute angle at C is two thirds the complement of the acute angle at A, with opposite sides a, b, c, we have

$b^{2}=c^{2}+ab\,$

or

${\frac {b}{c}}={\frac {c}{b-a}}.$

Some Pythagoras-related things:

• Pythagoras' theorem
• Pythagorean triple
• Pythagorean trigonometric identity
• Dulcarnon
• Kātyāyana
• Nonhypotenuse number
• Parallelogram law
• Treatment of Pythagoras' theorem in rational trigonometry
• Synthetic geometry
• Triangle
• Pythagorean expectation
• Ptolemy's theorem