Articles containing proofs | Theorems about quadrilaterals and circles

Brahmagupta theorem

In geometry, Brahmagupta's theorem states that if a cyclic quadrilateral is orthodiagonal (that is, has perpendicular diagonals), then the perpendicular to a side from the point of intersection of the diagonals always bisects the opposite side. It is named after the Indian mathematician Brahmagupta (598-668). More specifically, let A, B, C and D be four points on a circle such that the lines AC and BD are perpendicular. Denote the intersection of AC and BD by M. Drop the perpendicular from M to the line BC, calling the intersection E. Let F be the intersection of the line EM and the edge AD. Then, the theorem states that F is the midpoint AD. (Wikipedia).

Brahmagupta theorem
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A New Proof of Bhramagupta’s Formula

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From playlist Summer of Math Exposition Youtube Videos

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Brahmagupta's formula and the Quadruple Quad Formula (II) | Rational Geometry Math Foundations 126

The classical Brahmaguptas' formula gives the area for a convex cyclic quadrilateral, in terms of the four side lengths. We want to connect this with the purely 1-dimensional result called the Quadruple Quad Formula. First we review the corresponding relation between Heron's formula and th

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Brahmagupta's formula and the Quadruple Quad Formula (I) | Rational Geometry Math Foundations 125

In this video we introduce Brahmagupta's celebrated formula for the area of a cyclic quadrilateral in terms of the four sides. This is an obvious extension of Heron's formula. We are interested in finding a rational variant of it, that will be independent of a prior theory of `real numbers

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The Bretschneider von Staudt formula for a quadrilateral | Rational Geometry Math Foundations 132

Brahmagupta's formula gives the area of a cyclic quadrilateral in terms of its four (outside) `lengths', and the CQQ theorem was a logically correct reformulation of that result, using quadrances instead of `distances'. But what about a general quadrilateral? This is a redo of last week's

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Heron’s formula: What is the hidden meaning of 1 + 2 + 3 = 1 x 2 x 3 ?

Today's video is about Heron's famous formula and Brahmagupta's and Bretschneider's extensions of this formula and what these formulas have to do with that curious identity 1+2+3=1x2x3. 00:00 Intro 01:01 1+2+3=1x2x3 in action 02:11 Equilateral triangle 02:30 Golden triangle 03:09 Chapter

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History of Indian Mathematics Part II: Brahmagupta, Algebra, and Zero

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You've never seen imaginary numbers like this before

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Who invented zero? | India and The Divinity of Numbers | Math and the Rise of Civilization

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The Cyclic quadrilateral quadrea theorem | Rational Geometry Math Foundations 127a | NJ Wildberger

The Cyclic quadrilateral quadrea (CQQ) theorem is a major re-evaluation of the classical theorem of Brahmagupta on the area of a convex cyclic quadrilateral, which combines it with Robbins much more recent formula for the corresponding area of a non-convex cyclic quadrilateral. We illustr

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The Cyclic quadrilateral quadrea theorem (cont.) | Rational Geometry Math Foundations 127b

The Cyclic quadrilateral quadrea (CQQ) theorem is a major re-evaluation of the classical theorem of Brahmagupta on the area of a convex cyclic quadrilateral, which combines it with Robbins much more recent formula for the corresponding area of a non-convex cyclic quadrilateral. We exhibit

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Pythagorean Theorem VIII (Bhāskara's visual proof)

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Related pages

Midpoint | Cyclic quadrilateral | Brahmagupta's formula | Perpendicular | Bisection | Geometry | Orthodiagonal quadrilateral | Inscribed angle | Isosceles triangle