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
You may need to sit down with your parents or with your teacher and
go over how to add and subtract fractions.
1). "Perimeter" means the distance all the way around the square.
With a square, all 4 sides are the same length. With <u>this</u> square,
every side is 1-1/4 inches long.
Perimeter = length of all 4 sides= (1-1/4) + (1-1/4) + (1-1/4) + (1-1/4) =
(1 + 1 + 1 + 1) + (1/4 + 1/4 + 1/4 + 1/4) =
4 + 4/4 = <em>5 inches</em> .
2). (2-3/8) + (1-7/8) = (2 + 1) + (3/8 + 7/8) =
(3) + (10/8) =
3 + 1-1/4 = <em>4-1/4 .</em>
3). The difference is (1-1/6) minus (5/6) .
Before you start to do the subtraction, write the (1-1/6) as (7/6) .
Then the subtraction is (7/6) - (5/6) = 2/6 = <em>1/3</em> .
4). This one is almost the same kind of problem as #3.
It's another subtraction.
If you need (2-1/4) all together, and you already have (1-3/8),
then the amount you still have to find, or borrow, or buy, is the
difference between those two numbers.
(2-1/4) minus (1-3/8) .
The trick is to write the (2-1/4) in some form that you'll be able to
subtract (1-3/8) from it. When I learned how to do that, it was called
'borrowing', but I think now it's called 'regrouping'.
We need to work on (2-1/4):
-- take 1 from the 2, and change it into fourths.
2-1/4 = 1 and 4/4 and 1/4 = 1 and 5/4
-- Now, take those 5/4, and turn them into eighths.
Each fourth makes 2 eighths. So 5/4 = 10/8.
Now, the (2-1/4) has turned into 1-10/8 .
We did NOT change the value. It's still the same amount
as 2-1/4 , but it's just written in a different way.
And now the subtraction is easy:
(2-1/4) minus (1-3/8) =
(1-10/8) minus (1-3/8) = (zero and 7/8).
You need <em>7/8 inch</em> more string than you already have.
*☆*――*☆*――*☆*――*☆*――*☆*――*☆*――*☆*――*☆**☆*――*☆*――*☆*――*☆
Answer: To finish the sample you need the term, 1.5 Then the sample is done!
I hope this helped!
<!> Brainliest is appreciated! <!>
- Zack Slocum
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Answer:
The independent is the weight of all the people already on the elevator and the dependent variable is the weight of the elevator after you get on.
