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Angles

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Angles

By Mr. Bales

- 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.

- 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!!
- NBA
- So, how many degrees are there in a full turn?

- The 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.

- 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.

270°

1/2 turn

¼ turn

90°

180°

full turn

¾ turn

360°

- Let’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?

A

How would you label this Daniella?

B

C

- Anglesare 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.

Perfect! < ABC or < CBA

Always label angles with vertex in the middle!

S

Can you label this correctly?

T

U

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

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

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

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

Bales Bucks!!!

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