Question

You can use the formula A = C/4 to find the area of a circle given the circumstance. Describe another way to find the area of a circle when given the circumstance. Help please!

Answer 1

`A = (Cr)/(2)`

Explanation:

Given

`A = (C)/(4)`

Required

Describe another way to get area from circumference

Circumference C is calculated using:

`C = 2\pi r`

Area, A is calculated using:

`A = \pi r^2`

Using:
`C = 2\pi r`

Divide both sides by 2

`(C)/(2) = (2\pi r)/(2)`

`(C)/(2) = \pi r`

Multiply both sides by r

`r*(C)/(2) = \pi r*r`

`r*(C)/(2) = \pi r^2`

`(Cr)/(2) = \pi r^2`

The expression on the right-hand side is the area.

So, substitute
`\pi r^2` for A

`(Cr)/(2) = A`

Reorder

`A = (Cr)/(2)`