Lesson 1: Introduction to Circles, Arcs and Angles

Introduction to Circles

(Arcs & Angles​)

By: Rinalyn Saballe

Arcs: minor , semicircle, major arc

• minor arc - n arc measuring less than 180°

• ​semicircle - An arc measuring exactly 180° or π radians, which excludes designating either part of the circle as major or minor.

• major arc - ​An arc measuring greater than 180° but less than 360.

Angles: central and inscribed angles

• central angle - A central angle is the angle that forms when two radii meet at the center of a circle

• inscribed angle - ​An inscribed angle is an angle whose vertex lies on the circumference of a circle while its two sides are chords of the same circle

• m of central angle = m of intercepted arc

  ​

• ​m of inscribed angle= 1/2(intercepted arc)

Lesson 1: Introduction to Circles

Arcs - Central Angles -Inscribed Angles

Let's have some brain teasers!

Lesson 1: Introduction to Circles

Open Ended

Name two major arcs.

Open Ended

Name two minor arcs.

Poll

$$\angle$$  HAT is an acute angle.

• TRUE

• FALSE

Multiple Choice

Given the figure, which of the following is an obtuse central angle? 

• $$\angle$$  MAH

• $$\angle$$  HAT

• $$\angle$$  MAT

Fill in the Blanks

Name a radius that is not part of the diameter.

Multiple Choice

Which of the following is a semicircle?

• arc MHT

• arc MTH

• arc HT

Multiple Choice

What is the measurement of arc HT?

• 180 $$\degree$$  

• 50 $$\degree$$  

• 130 $$\degree$$  

Multiple Choice

Compute for the m $$\angle$$ MAH.

• 50 $$\degree$$  

• 20 $$\degree$$  

• 130 $$\degree$$  

Multiple Choice

What is the measurement of arc MH?

• 50 $$\degree$$  

• 20 $$\degree$$  

• 130 $$\degree$$  

Multiple Choice

What is the measurement of arc HMT?

• 310 $$\degree$$  

• 220 $$\degree$$  

• 270 $$\degree$$  

ARCS- CHORDS RELATIONSHIP

Lesson 1: Introduction to Circles

ARCS- CHORDS RELATIONSHIP

Lesson 1: Introduction to Circles

Fill in the Blanks

Find the value of x.

Multiple Choice

What is the measurement of x?

• 30 $$\degree$$  

• 90 $$\degree$$  

• 50 $$\degree$$  

Fill in the Blanks

What is the value of x?

Multiple Choice

What is the value of x?

• 24

• 48

• 32