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: First let’s find x.
A straight line adds up to 180 degrees. So wen know that X and the 81 degree angle should add up to 180, so x+81=180 is our equation. Let’s solve.
Subtract 81 from 180
You get x=99 degrees.
Let’s now find Y.
We know because of the alternate interior angles property that x will have to equal 3y-9. We already know x is 99. Let’s set up an equation. 3y-9=99 let’s add our 9. We get 108. Divide by 3. We get y=36.
Step-by-step explanation:
PLEASE ASK ANY FURTHER QUESTIONS IF YOU STILL DONT UNDERSTAND :)
√8+√18−√32
√2^2·2+√3^2·2−√2^4·2
√2^ 2·√2+√3^2·√2−√2^4·√2
√2 is the answer
