Angles

By Mr. Bales

Objective

By the end of this lesson, you will be able to identify, describe, and classify angles.Standard 4MG3.5 - Students need to know the definitions of a right angle, an acute angle, and an obtuse angle. Understand that 90°, 180°, 270°, and 360° are associated respectively, with 1/4, 1/2, 3/4, and full turns.

Turns

How many degrees does it take to go in a complete circle? Or make one full turn?Let’s watch a little NBA to find out!!NBASo, how many degrees are there in a full turn?

History LessonThe Babylonians in about 2400 B.C. lived in Mesopotamia, now southern Iraq. They used a number system based on 60. Some believe they divided the circle into 360 degrees because 6 x 60 = 360 degrees. Others believed that they watched the planets and the sun. They knew it took 360 days for the sun’s path to complete a total circuit. Either way, that is how we got the 360 degree circle.

Get Ready to Learn

MJ’s teacher (that’s me) assigned ten problems for homework. MJ started his homework at 4:00 p.m. He completed it at 4:15 p.m. How far has the minute hand turned?Use the following pictures to help you solve the problem.

More on Turns

90°¼ turn

270°

¾ turn

180°1/2 turn

full turn

360°

ActivityLet’s get on our feet and practice this!!Please stand and face the board, which is 12:00.Turn 1/4 turn.What angle measure is that?Turn 1/2 turn.What angle measure is that?Turn 3/4 turn.What angle measure is that?Turn a full turn.What angle measure is that?

What are Angles?

Angles are figures that are formed by two rays or two line segments with a common endpoint.You label angles with a < symbol and you place the vertex in the middle of the three points.

Always label angles with vertex in the middle!

A

B

C

How would you label this Daniella?

Perfect! < ABC or < CBA

Right Angles

There are all kinds of different angles.A right angle has a “square corner”.

UT

SCan you label this correctly?

Acute Angles

An acute angle measures greater than 0º and less than 90º.

Obtuse Angles

An obtuse angle measures greater than 90º, but less than 180º.

More on Angles

Let’s hear from Mr. Hardesty as he explains a few different angles.Mr. Hardesty!!

Bales Bucks!!!

Assignment

Page 400 - #’s 8 - 19Get them all correct, No Math Homework