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:
110.5mm
Step-by-step explanation:
Formula : a = hb/2
a = 13(17)/2
221/2 = 110.5
Answer
Step-by-step explanation:
A=2πrh+2πr2=2·π·3·6+2·π·32≈169.646
A/78 = 25/100 . . . . the equation
a = 78*25/100 = 19.5
19.5 is 25% of 78
Answer:
The Answer is C.
Step-by-step explanation:
