Circumference of a circle - derivation
This page describes how to derive the formula for the circumference of a circle.
Recall that the definition of pi (π) is the circumference c of any circle divided by its diameter d. Put as an equation, pi is defined as
π
=
c
d
Rearranging this to solve for c we get
c
=
π
d
The diameter of a circle is twice its radius, so substituting 2r for d
c
=
2
π
r
If you know the area
Recall that the area of a circle is given by
area
=
π
r
2
Solving this for r
r
2
=
a
π
So
r
=
√
a
π
The circumference c of a circle is
c
=
2
π
r
Answer:
x = 3 ± 
Step-by-step explanation:
x² - 6x - 4 = 0 ( add 4 to both sides )
x² - 6x = 4
To complete the square
add ( half the coefficient of the x- term)² to both sides
x² + 2(- 3)x + 9 = 4 + 9
(x - 3)² = 13 ( take square root of both sides )
x - 3 = ± ( add 3 to both sides )
x = 3 ±
Answer:
Step-by-step explanation:9m -3m +2n = 6m+2n
Answer:
slope: 2/5
Step-by-step explanation:
3 1/2
x365
Write that down and figrue it its pretty simple.
