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In geometry, the circumference (from Latin circumferens, meaning "carrying around") is the perimeter of a circle or ellipse. The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment . [ 1 ]
The ratio of a circle's circumference to its diameter is π (pi), an irrational constant approximately equal to 3.141592654. The ratio of a circle's circumference to its radius is 2 π . [ a ] Thus the circumference C is related to the radius r and diameter d by: C = 2 π r = π d . {\displaystyle C=2\pi r=\pi d.}
The French scale measures and is proportional to the outer diameter of a catheter, with 1 French (Fr) defined as 1 ⁄ 3 millimeter, making the relationship: 1 mm = 3 Fr. Thus, the outer diameter of a catheter in millimeters can be calculated by dividing the French size by 3. [2]
Earth's circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi). [1] Treating the Earth as a sphere, its circumference would be its single most important measurement. [2]
The hydraulic diameter is the equivalent circular configuration with the same circumference as the wetted perimeter. The area of a circle of radius R is π R 2 {\displaystyle \pi R^{2}} . Given the area of a non-circular object A , one can calculate its area-equivalent radius by setting
Let A′ be the point opposite A on the circle, so that A′A is a diameter, and A′AB is an inscribed triangle on a diameter. By Thales' theorem , this is a right triangle with right angle at B. Let the length of A′B be c n , which we call the complement of s n ; thus c n 2 + s n 2 = (2 r ) 2 .
The perimeter of a circle or an ellipse is called its circumference. Calculating the perimeter has several practical applications. A calculated perimeter is the length of fence required to surround a yard or garden. The perimeter of a wheel/circle (its circumference) describes how far it will roll in one revolution. Similarly, the amount of ...
In square mils, the area of a circle with a diameter of 1 mil is: = = = = ( ) = . By definition, this area is also equal to 1 circular mil, so = . The conversion factor from square mils to circular mils is therefore 4/ π cmil per square mil: