Pi is defined as the ratio of the circumference of a circle to the diameter of the circle.
Therefore, if you measure the diameter of the circle (call it 'D') then the circumference of the circle is pi times D.
To find the area of the circle use the formula Area = pi* D2 /4 .
Going one step further, to a sphere, if you measure the radius of the sphere (call it R, where R is half the diameter D), then:
1) The surface area of the sphere is Area = 4 * pi * R2 .
2) The volume of the sphere is Volume = (4/3) * pi * R3 .
Pi (3.141...) is used for circles, and circles only. You use it to find the area and circumfrence.
WHEN THE TEACHER TELLS YOU THAT YOU NEED TO USE PI...SORRY THAT'S ALL I CAN ANSWER FOR YOU...LATERZWhen you use chords, diameter, and radii in circles
People all around America still use Archimedes discoveries today. Like The snail screw we use that to raise and move water. Another discovery from Archimedes we use today is pi. We use pi to find the circumference for circles. Everyone should use the "Principles of Archimedes" because we use that to weigh objects.
The distance around the outside of a circle is called the circumference. You can find this difference by multiplying the circles diameter by pi (3.141...).
circumference = pi * 2radius (diameter) so to find radius you use circumference/(2 x pi) this will find radius ----
Pi (3.141...) is used for circles, and circles only. You use it to find the area and circumfrence.
You use pi to find volumes that include circles, as volume = area x depth, and the area of a circle always involves pi
Formulas relating to circles
To calculate properties of circles
Pi is very important for finding circumfrences and area's of circles.
Circumference of any circle = 2*pi*radius or pi*diameter
Pi times the diameter of a circle gives its circumference.
Volume = 4/3 * pi * radius3'Pi' is just a number. It doesn't 'do' anything, any more than '6' does. The specialthing about 'pi' is that it's the number that keeps popping up wherever circles areinvolved. So if a person is paying attention, it doesn't take him long to realize thathe can use 'pi' to do things, like with angles, and with things that move in circles,and like finding the area of circles and the volume of spheres.It's not the 'pi' that does it. It's the person who knows how to use the number 'pi'.
Pi is an experimentally found value that always works for circles, so we use it. Mathematical pi is not pie. it is a Greek letter pi.
The circumference of a circle = pi*diametre = 2pi*radius
Area=pi times radius squared Circumference=pi times diameter or pi times radius times two
Working out areas and volumes of circles and spheres respectively