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West Asian mathematics – history of math

By |2018-05-10T10:12:08-07:00September 16th, 2017|Science, West Asia|

History of math: Sumerian multiplication table (2700 BC) Cuneiform multiplication table Once people in West Asia figured out how to write down numbers, about 3500 BC, they quickly began to want to use cuneiform to write down other mathematical ideas. (Read more about the invention of numbers) The earliest example of this that we have is from about 2700 BC. It [...]

What is centrifugal force? Physics definitions

By |2019-03-11T05:58:01-07:00August 16th, 2017|Islam, Physics|

Kids playing tetherball using centrifugal force Who first explained centrifugal force? When something is going straight, it always keeps going straight unless something else stops it or turns it. (The Iranian scientist Ibn Sina figured this out about 1000 AD). Who was Ibn Sina? Medieval Islamic science All our physics articles An example of centrifugal [...]

Tangents – trigonometry – math

By |2018-04-11T09:30:18-07:00July 29th, 2017|Math|

Tangents: This line is tangent to a circle. What is a tangent? A tangent, like a sine or a cosine, is a mathematical way of thinking about a kind of movement that happens in nature. A tangent is really just a rephrasing of the same information we already had for calculating the sine function. Lines and circles [...]

Area of a sphere – Volume of a sphere

By |2017-07-29T13:10:50-07:00July 29th, 2017|Math|

This is a sphere. A sphere is a three-dimensional circle. Or you could say that a sphere is the set of all the points that are at the same distance from the center of the sphere. In nature, centrifugal force and gravity tend to make a lot of things into spheres: soap bubbles, for instance, atoms, and planets. The radius of a sphere [...]

What is a radius? Radius of a circle

By |2018-05-10T10:38:52-07:00July 29th, 2017|Math|

What is a radius? The geometry of a circle What is a radius? The radius of a circle is the distance from the center point to the edge of the circle. It's the same distance anywhere on the circle, because the circle has radial symmetry. So it doesn't matter where you measure the radius on the circle, [...]

What is pi? Simple geometry – Math, circles, circumference, diameter

By |2018-04-23T16:01:03-07:00July 29th, 2017|Math|

What is pi? The geometry of a circle What is pi? Pi is a number that is just a little bigger than 3.14. It is the number you get if you divide the circumference of any circle by its diameter. It's the same for all circles. You can approximate pi for yourself by taking some circular things like the tops [...]

Equilateral triangle – Simple geometry

By |2017-07-29T09:56:35-07:00July 29th, 2017|Math|

This is an equilateral triangle. Equilateral triangles have all three sides exactly the same length. Because their sides are the same length, the three angles of an equilateral triangle are also all the same size, so they're each one third of 180 degrees, or 60 degrees. All three angles of any equilateral triangle are 60 degrees, no matter how [...]

Checking the surface area of a sphere

By |2017-07-29T09:44:05-07:00July 29th, 2017|Math|

Did you ever have to wrap a basketball as a present? To see how the surface area of a sphere is really 4πr2, find a ball to wrap (a basketball works well). Cut some wrapping paper to fit the ball. Then you'll need to measure the circumference of the ball. You could wrap a piece of string around [...]