Find the value of x. Round to the nearest
tenten-thousandth.
What do you know about circles?
10.1 – Circles &
Circumference
Learning Target 1: to be able to identify and use parts of circles
Learning Target 2: to be able to solve problems involving the circumference of a circle.
Circle – the set of all points in a plane equidistant from a
given point called the center of the circle.
C
You name a circle after it’s center!
center
Parts of a Circle…
Radius – is a segment with endpoints
at the center and on the circle.
B
A
Chord – is a segment with endpoints
on the circle.
D
Diameter – is a chord that passes
through the center and is made up
of collinear radii.
C
E
F
Parts of a Circle…
Name the circle, then identify a radius, a chord, and a
diameter on each.
Circle:
Circle:
Circle:
Radius:
Radius:
Radius:
Chord:
Chord:
Chord:
Diameter:
Diameter:
Diameter:
Radius & Diameter…
The radius of a circle is half the length of the diameter.
So… if a circle has radius r and diameter d, the following
relationships are true…
d
r=
2
and d = 2r
Radius & Diameter…
State the radius and diameter of each circle.
4
22
13
7
r =
r =
r =
r =
d =
d =
d =
d =
Area & Circumference…
Area – the number of square units inside a circle.
A =πr
2
Circumference – the distance around a circle.
C = π d or C = 2π r
How are these the same?
Area & Circumference…
Find the area and circumference of each circle. Round your answer to
the nearest tenth.
6
30
Area & Circumference…
2
Given a circle’s area is 452.2 in , find circumference. Round
to the nearest hundredth.
Given a circle’s circumference is 37.7 km, find the area.
Round to the nearest tenth.
Circle Pairs…
Two circles are Congruent Circles if and only if that have
congruent radii.
2
2
Concentric Circles are coplanar circles that have the same
center.
Intersecting Circles…
The diameter of circle S is 30, the diameter of circle R is
20, and DS = 9. Find CD and RC.
Intersecting Circles…
The diameter of circle X is 22, the diameter of circle Y is 16,
and WZ = 5. Find XY.
Inscribed in a Circle…
A polygon is inscribed in a circle if all of its vertices lie on
the circle.
A circle is circumscribed about a polygon if it contains all
the vertices of the polygon.
Inscribed in a Circle…
The triangle is inscribed in the circle below. Find the exact
circumference of the circle.
Inscribed in a Circle…
The circle is inscribed within a square. Find the area of the
circle. Leave your answer in terms of pi.
Inscribed in a Circle…
How would you find the area of the shaded region?? Round to the
nearest hundredth.
Homework ☺
WS
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