Unit Circle (3B): Introduction (circle review)

Unit Circle:

Review-Parts of the Circles

Lesson Objective:

• To enable students to become familiar with the unit circle

• To use the unit circle to evaluate the trigonometric functions sin, cos and tan for all angles

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DEFINITION: a line that goes from the center of the circle to any point on the circle

FORMULA: Radius = Diameter divided by 2

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Unit 4B - Circles - Math 7

RADIUS

DEFINITION: A straight line that goes from one side of a circle to the opposite side AND through the center of the circle.

FORMULA: Diameter = Radius x 2

Unit 4B - Circles - Math 7

​DIAMETER

Unit 4B - Circles - Math 7

CIRCUMFERENCE

Dropdown

A line that goes from the center of the circle to any point on the circle is called a ​

Select answer

.​ ​

Dropdown

A straight line that goes from one side of a circle to the opposite side AND through the center of the circle. is called ​

Select answer

​

​ ​ ​

Dropdown

The distance around the outside of the circle is called ​

Select answer

​ ​

Open Ended

Based on the diagram shown, how much radius makes a diameter?

DEFINITION: a ratio between the circumference and the diameter of a circle. It is approximately 3.14

FORMULA: Circumference divided by diameter

​

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Dropdown

The number of times that a ​

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can fit around a circle's ​

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is called ​

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. There are approximately ​

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diameters that can fit within the circumference of a circle.

Multiple Choice

What is a straight line that goes through the center of a circle from one side to the opposite side?

• Diameter

• Circumference

• Radius

• Center

Multiple Choice

Does this picture show the diameter or radius of a circle?

• Diameter

• Radius

Multiple Choice

What is the line that goes from the center of a circle to any point on the circle?

• Diameter

• Circumference

• Chord

• Radius

Multiple Choice

Is the red line the radius or the diameter of the circle?

• Radius

• Diameter

Multiple Choice

Is the red line the radius or the diameter of the circle?

• Radius

• Diameter

Multiple Choice

Is the red line the radius or the diameter of the circle?

• Radius

• Diameter

Multiple Choice

What is the radius of the circle?

• 18

• 72

• 38

• 14

Multiple Choice

What is the diameter of the circle?

• 8

• 16

• 10

• 4

Multiple Choice

What is the diameter of the circle?

• 5 inches

• 10 inches

• 3.14 inches

• 15.84 inches

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The lesson on circle review is Complete!

We will next study the Unit Circle

Open Ended

Conduct a short Google search on the Unit Circle and write one thing you understand about unit circles.