Articles containing proofs | Theorems about quadrilaterals and circles
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).
A New Proof of Bhramagupta’s Formula
For years John Conway searched for an elegant, symmetric, and geometric proof of Brahmagupta’s formula. Here it is, presented by a team of students from Proof School!
From playlist Summer of Math Exposition Youtube Videos
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
From playlist Math Foundations
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
From playlist Math Foundations
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
From playlist Math Foundations
Calculus - The Fundamental Theorem, Part 1
The Fundamental Theorem of Calculus. First video in a short series on the topic. The theorem is stated and two simple examples are worked.
From playlist Calculus - The Fundamental Theorem of Calculus
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
From playlist Recent videos
Theory of numbers: Gauss's lemma
This lecture is part of an online undergraduate course on the theory of numbers. We describe Gauss's lemma which gives a useful criterion for whether a number n is a quadratic residue of a prime p. We work it out explicitly for n = -1, 2 and 3, and as an application prove some cases of Di
From playlist Theory of numbers
History of Indian Mathematics Part II: Brahmagupta, Algebra, and Zero
Ever wonder how zero evolved from placeholder to integer? Or about how the formula for the area of a cyclic quadrilateral was discovered? Then check out this video! And be sure to check out the rest of the series on the blog: https://centerofmathematics.blogspot.com/2019/11/history-of-indi
From playlist History of Indian Mathematics
Calculus 5.3 The Fundamental Theorem of Calculus
My notes are available at http://asherbroberts.com/ (so you can write along with me). Calculus: Early Transcendentals 8th Edition by James Stewart
From playlist Calculus
What Is The Area? Square Between Two Circles
Thanks to Nibedan Mukherjee who sent me the problem and its solution all the way back in October 2018. I was also told this problem appeared in the 2019 Senior Mathematical Challenge by the UKMT. 2019 Senior Mathematical Challenge paper (see question 25) https://www.ukmt.org.uk/sites/defa
From playlist Math Puzzles, Riddles And Brain Teasers
You've never seen imaginary numbers like this before
#some2 The material in this video is heavily inspired by Norman Wildberger's Youtube Channel. Go check it out! https://www.youtube.com/c/njwildberger/featured 0:00 Intro 1:23 2D symmetries 3:00 Matrix representation 5:04 Field 6:24 Quadratic Forms 8:34 Dot Product 11:20 Determinant 13:1
From playlist Summer of Math Exposition 2 videos
The Fundamental Theorem of Calculus | Algebraic Calculus One | Wild Egg
In this video we lay out the Fundamental Theorem of Calculus --from the point of view of the Algebraic Calculus. This key result, presented here for the very first time (!), shows how to generalize the Fundamental Formula of the Calculus which we presented a few videos ago, incorporating t
From playlist Algebraic Calculus One
Who invented zero? | India and The Divinity of Numbers | Math and the Rise of Civilization
Who invented zero in India? In 628 CE, astronomer-mathematician Brahmagupta wrote his text Brahma Sphuta Siddhanta which contained the first mathematical treatment of zero. He defined zero as the result of subtracting a number from itself, postulated negative numbers and discussed their pr
From playlist Civilization
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
From playlist Math Foundations
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
From playlist Math Foundations
Pythagorean Theorem VIII (Bhāskara's visual proof)
This is a short, animated visual proof of the Pythagorean theorem (the right triangle theorem) following essentially Bhāskara's proof (Behold!). This theorem states the square of the hypotenuse of a right triangle is equal to the sum of squares of the two other side lengths. #math #manim #
From playlist Pythagorean Theorem
What are complex numbers? | Essence of complex analysis #2
A complete guide to the basics of complex numbers. Feel free to pause and catch a breath if you feel like it - it's meant to be a crash course! Complex numbers are useful in basically all sorts of applications, because even in the real world, making things complex sometimes, oxymoronicall
From playlist Essence of complex analysis