Question

Suppose the circumference of a circle is
4π. What is its area?

Answer 1

\(\sf C = 2 \pi r\)

Find the radius first, then plug it into the formula to find the area.

Answer 2

Plug in what we know:

\(\sf 4 \pi = 2 \pi r\)

Divide 2 pi to both sides

Answer 3

What is the formula for the circumference? When you know this you have to solve for r then take the formula for the area of the circle and plug in r

Answer 4

\[\frac{ 4 \pi }{ 2 \pi } = \frac{ 2 \pi r }{ 2 \pi } \]

Answer 5

@iGreen does r=2

Answer 6

Yes!

Answer 7

yay!

Answer 8

Formula for the area of a circle:

\(\sf A = \pi r^2\)

Plug in 2 for the radius:

\(\sf A = \pi (2^2)\)

Answer 9

2^2 = ?

Answer 10

\[A=\pi(2^{2})=4 \times3.14= 6.28??\]

Answer 11

Yes, but I don't think they want you to simplify pi..

Answer 12

If they do, 6.28 is correct..but if they don't, it's \(\sf 4 \pi\).

Answer 13

ok i'll let know in a sec

Answer 14

ya its \[4 \pi\]

Answer 15

Thx so much i get this now i wrote down notes to understand @iGreen

Answer 16

Yay! \(\Huge\ddot\smile\)