How To Calculate The Circumference Of A Circle
Mathematics / Geometry
A circle is what you get if you take a straight line and bend it around so that its ends touch. You can demonstrate this by taking a piece of stiff wire and doing just that: bring the ends of the wire continue reading this fact

How To Calculate The Area Of A Circle
Mathematics / Geometry
A circle is the round counterpart of a square. To find the area of a square, one multiplies the length by the width. A circle doesn't have these, however, so there has to be a different way to calcula continue reading this fact

Unit Of Luminous Intensity (candela)
Mathematics / History
Originally, each country had its own, and rather poorly reproducible, unit of luminous intensity; it was necessary to wait until 1909 to see a beginning of unification on the international level, when continue reading this fact
