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Geometry

Harold R. Jacobs

Chapter 14

Regular Polygons and the Circle - all with Video Answers

Educators


Section 1

Regular Polygons

00:20

Problem 1

Tell whether each of the following statements is true or false.
Every triangle is cyclic.

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00:12

Problem 2

Tell whether each of the following statements is true or false.
If a triangle is equilateral, it must be regular.

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00:31

Problem 3

Tell whether each of the following statements is true or false.
If a quadrilateral is equilateral, it must be regular.

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00:33

Problem 4

Tell whether each of the following statements is true or false.
If a quadrilateral is equiangular, it must be regular.

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00:16

Problem 5

Tell whether each of the following statements is true or false.
If a quadrilateral is equiangular, it must be cyclic.

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00:10

Problem 6

Tell whether each of the following statements is true or false.
If a polygon is regular, it must be convex.

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00:08

Problem 7

Tell whether each of the following statements is true or false.
If a polygon is regular, it must be cyclic.

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00:11

Problem 8

Tell whether each of the following statements is true or false.
If a polygon is cyclic, it must be regular.

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00:23

Problem 9

Tell whether each of the following statements is true or false.
If a polygon is regular, it must be equilateral.

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00:14

Problem 10

Tell whether each of the following statements is true or false.
If a polygon is equilateral, it must be equiangular.

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00:09

Problem 11

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
What is point O called with respect to the pentagon?

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00:11

Problem 12

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
What is $\overline{\mathrm{OG}}$ called?

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00:53

Problem 13

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
How do we know that $\overline{\text { OG }}$ bisects $\overline{\mathrm{RE}}$ ?

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00:12

Problem 14

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
What are $\overline{\mathrm{OR}}$ and $\overline{\mathrm{OE}}$ called with respect to NITRE?

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00:18

Problem 15

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
What kind of triangle is $\triangle O R E ?$

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00:12

Problem 16

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
What is $\underline{x}ROE$ called with respect to NITRE?

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00:11

Problem 17

Circle $\mathrm{O}$ is circumscribed about regular pentagon NITRE; $\overline{\mathrm{OG}} \perp \overline{\mathrm{RE}}$.
(IMAGE CAN'T COPY)
Does $\overrightarrow{\mathrm{OG}}$ bisect $\underline{x}\mathrm{ROE} ?$

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00:22

Problem 18

The figures below illustrate the central angles of some regular polygons.
(IMAGE CAN'T COPY)
As the number of sides of a regular polygon increases, how does the measure of one of its central angles change?

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00:57

Problem 19

The figures below illustrate the central angles of some regular polygons.
(IMAGE CAN'T COPY)
Find the measure of a central angle of each figure shown.

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00:12

Problem 20

The figures below illustrate the central angles of some regular polygons.
(IMAGE CAN'T COPY)
Find the measure of a central angle of a regular decagon.

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00:29

Problem 21

The figures below illustrate the central angles of some regular polygons.
(IMAGE CAN'T COPY)
How would you express the measure of a central angle of a regular polygon that has $n$ sides in terms of $n ?$

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00:26

Problem 22

The figure below suggests a way to construct a regular hexagon.
(IMAGE CAN'T COPY)
What kind of triangles surround point $O ?$

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00:54

Problem 23

The figure below suggests a way to construct a regular hexagon.
(IMAGE CAN'T COPY)
How do the sides of the hexagon compare in length to the radius of the circle?

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01:44

Problem 24

The figure below suggests a way to construct a regular hexagon.
(IMAGE CAN'T COPY)
Use your straightedge and compass to construct a regular hexagon by inscribing it in a circle.

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00:16

Problem 25

The figure below suggests a way to construct a square.
(IMAGE CAN'T COPY)
What relation do $\overline{\mathrm{AC}}$ and $\overline{\mathrm{BD}}$ have to each other?

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02:38

Problem 26

The figure below suggests a way to construct a square.
(IMAGE CAN'T COPY)
Use your straightedge and compass to construct a square by inscribing it in a circle.

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04:02

Problem 27

The figure below suggests a way to construct a square.
(IMAGE CAN'T COPY)
Construct a regular octagon. (Hint: Begin by inscribing a square in a circle.)

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03:29

Problem 28

The figure below suggests a way to construct a square.
(IMAGE CAN'T COPY)
Construct a regular dodecagon. (Hint: Begin by inscribing a regular hexagon in a circle.)

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00:56

Problem 29

In the figure below, $\overline{\mathrm{OT}}$ is an apothem of regular pentagon KRYPN; $\angle \mathrm{O}=36^{\circ}$ and $\mathrm{ON}=10 .$ Use the appropriate trigonometric
(IMAGE CAN'T COPY)
$OT$

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01:03

Problem 30

In the figure below, $\overline{\mathrm{OT}}$ is an apothem of regular pentagon KRYPN; $\angle \mathrm{O}=36^{\circ}$ and $\mathrm{ON}=10 .$ Use the appropriate trigonometric
(IMAGE CAN'T COPY)
$NT$

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01:29

Problem 31

(IMAGE CAN'T COPY)
Given: FLUORINE is a regular polygon with diagonals $\overline{\mathrm{NR}}$ and $\overline{\mathrm{RU}}$
Prove: $ \mathrm{NR}=\mathrm{RU}$

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01:43

Problem 32

(IMAGE CAN'T COPY)
Given: $\mathrm{XYGEN}$ is a regular polygon with central angles 1 and 2
Prove: $\angle 1=\angle 2$. (Hint: circumscribe circle $\mathrm{O}$ about XYGEN.)

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01:43

Problem 33

(IMAGE CAN'T COPY)
Given: CHLRINE is a regular polygon with center O. Prove: $\overrightarrow{\mathrm{LO}}$ bisects $\underline{x} \mathrm{HLR}$.

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02:40

Problem 34

(IMAGE CAN'T COPY)
Given: HELIUM is a regular hexagon with diagonals $\overline{\mathrm{HL}}$ and $\overline{\mathrm{MI}}$
Prove: $\overline{\mathrm{HL}} \| \overline{\mathrm{MI}}$ without adding anything to the figure.

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