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 [...]
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 [...]
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 [...]
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 [...]
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 [...]
What is a point? A circle is the set of points in a plane that are all the same distance away from a center point. What is a point? A [...]
A plane goes on infinitely in all directions. Just as a line is made of an infinite number of points, a plane is made of an infinite number of lines that are right [...]
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 [...]
This is an equilateral triangle. What makes a triangle equilateral? 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 [...]
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 [...]
