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Trigonometric identities are equalities that involve trigonometric functions and are true for every single value of the occurring variables. Geometrically, ... more

The area of an arbitrary triangle can be calculated from the two sides of the triangle and the included angle.
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In physics, Babinet’s principle states that the diffraction pattern from an opaque body is identical to that from a hole of the same size and shape ... more

Ceva’s theorem is a theorem about triangles in Euclidean plane geometry. Given a triangle ABC, let the lines AO, BO and CO ... more

Menelaus’ theorem, named for Menelaus of Alexandria, is a theorem about triangles in plane geometry. Given a triangle ABC, ... more

Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point ... more

Generalization of the Pythagorean theorem for the side opposite of the acute angle of an arbitrary triangle

Generalization of the Pythagorean theorem for the side opposite of the obtuse angle of an arbitrary triangle

A spherical wedge or ungula is a portion of a ball bounded by two plane semidisks and a spherical lune (termed the wedge’s base). The angle between ... more

In geometry, Heron’s formula (sometimes called Hero’s formula), named after Hero of Alexandria, gives the area of a triangle by requiring no ... more