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### Course: 4th grade (Eureka Math/EngageNY) > Unit 4

Lesson 1: Topic A: Line and angles- Terms & labels in geometry
- Lines, line segments, & rays
- Identify points, lines, line segments, rays, and angles
- Lines, line segments, and rays review
- Angles: introduction
- Angle basics
- Angle basics review
- Estimate angle measures
- Naming angles
- Name angles
- Types of angles by measure
- Recognizing angles
- Recognize angles in figures
- Acute, right, & obtuse angles
- Angle types
- Drawing acute, right and obtuse angles
- Angle types review
- Parallel & perpendicular lines intro
- Parallel & perpendicular lines
- Identify parallel and perpendicular lines
- Drawing parallel line segments
- Draw parallel and perpendicular lines
- Parallel and perpendicular lines review

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# Angle basics review

Review what an angle is and how an angle is measured.

### What is an angle?

An angle is two rays that share a ${\text{vertex}}$ .

Intersecting lines or line segments also form angles.

## Practice: Identifying an angle

## Measuring angles

Angles are measured in degrees.

The wider an angle is open, the greater its measure. If you compare these two angles, the first one is open wider.

So, the measure of this angle

is greater than the measure of this angle.

## Want to join the conversation?

- What is a Vertex?(79 votes)
- the vertex of an angle is the point where the rays or line segments meet.(146 votes)

- So, do angles relate to shapes like squares and circles?(41 votes)
- why is B used more than A in these questions?(26 votes)
- I'm not sure.

thank you for making me notice that(16 votes)

- At11:00how do I practice to get better at noticing angles, can khan academy help me with that(19 votes)
- A place where two rays meet is called an angle.(9 votes)

- why are angels measured in degress(20 votes)
- the babylonians (an ancient civilization, like Greeks) invented the 360 degree value which is the maximum an angle can be (which is a complete circle and after that, it kinda repeats on itself and the value of the angle gets even bigger). It's based on their base 60 counting (/number) system. There also exist other ways like radian ( angles are measured in pi) and tau (basically, "2*radians" tau = 2pi.)(9 votes)

- how do you measure an angle(14 votes)
- ABC angle would measure how far A to C is(13 votes)

- what is a plane figure(14 votes)
- why are you not showing if it is a right angle or something like that?(16 votes)
- Because you need to figure it out yourself(5 votes)

- I did not know it my teacher did not Teach me this.(13 votes)
- Maybe you were out someday when she taught it. Anyway, Right angle=90 degrees, Obtuse angle=more than 90, acute angle=less than 90.(6 votes)

- but if the wider angle is greater then what is a circle(9 votes)
- 360 is a circle’s angle.(9 votes)