## What is the radius If the circumference is 2pi?

The circumference of a circle can be found using the formula C=2𝜋r or C=𝜋d. We know the radius of the back wheel is 9 inches, so we can plug this into the formula C=2𝜋r. The formula becomes C=2𝜋(9) which simplifies to 56.52.

What is 2 pi r in circle?

2 pi r is the way to find the circumference when you have the radius.

Why is circumference 2pi r?

It sounds like you are aware of this, but just to clarify: the formulae 2πr and πd for the circumference of the circle are equivalent because the diameter is twice the radius. The former statement is often more useful simply because the radius of a circle is a property that we often refer to.

### What is the circumference with radius of 2?

To calculate the circumference, you need the radius of the circle: Multiply the radius by 2 to get the diameter. Multiply the result by π, or 3.14 for an estimation. That’s it; you found the circumference of the circle.

What is the circumference of this circle 2km?

The circumference of the circle is 12.56 km What is the perimeter of its sector whose central angle is 135°?

Why is 2 pi r squared?

Why is the area of a circle pi times the square of the radius? The usual definition of pi is the ratio of the circumference of a circle to its diameter, so that the circumference of a circle is pi times the diameter, or 2 pi times the radius.

#### What are the 2 circumference formulas?

Formula 1: When the radius of a circle is known. Formula 2: When the diameter of a circle is known….Summary.

Circumference of Circle 2πr
Perimeter of semi-circle πr + 2r
Area of semi-circle πr2/2

Why is it pi r squared?

By dividing the circle into more and more slices, the approximating parallelograms approximate the area of the circle arbitrarily close. This give a geometric justification that the area of a circle really is “pi r squared”.

Is it pi * r 2 or pi * r 2?

Pi is sometimes given the value 22 over 7 which is approximately 3.14. For a more accurate approximation, you should have a pi button on your calculator. The formula for area equals pi times the radius squared, R stands for the radius measurement of the circle. So the formula is area equals pi R squared.