# Circles - Sophia ```Important Info.
You’ll need: notebook, pencil, and formula card.
Pause. Rewind. Volume.
Questions?
Area &amp; Perimeter
Area: Covering
Perimeter: Surrounding
Polygons: Triangles, Rectangles, Squares,
Parallelograms, Trapezoids
What is a circle?
Not a polygon.
A plane figure with three or more straight sides
and angles.
Definition: a closed plane figure made up of all
the points the same distance from a point
called the center.
F
G
E
H
EF = EG = EH
Circle E
F
&frac12;
E
&frac12;
diameter
EF + EI = IF
I
Circle E
r+r=d
2r = d
Things You Should Know...
Diameter
A straight line from the
center of a circle to it
circumference.
A straight line passing through
the center of a circle connecting
2 points on the circumference.
It is half of the diameter.
Diameter = d
Circumference
Distance
around a circle.
C=2πr or
C=πd
π = 22/7 ≈ 3.14
Finding Circumference
C=2πr
Use this formula
when you are given
C=πd
Use this formula
when you are given
the diameter.
Find the circumference of each circle. Use 3.14 for π.
4 cm
Find the circumference of each circle. Use 3.14 for π.
6 in
Find the circumference of each circle. Use 3.14 for π.
Find the circumference of each circle. Use 3.14 for π.
Questions
Email:
[email protected]
[email protected]
[email protected]
Before school tomorrow.
Extra help on Mondays and Wednesdays.
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