Recognize Angles as Geometric Shapes Formed by Two Rays

Students learn that an angle is a geometric shape formed when two rays share a common endpoint called a vertex. Students identify angles in two-dimensional figures and in real-world objects, and distinguish angles from other geometric figures.

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Grade 4 · Understanding Angles · question 1 of 3

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20 rungs. A star at the top.

Count every angle in the tent flap.

Your answer:

How it is taught

0:00 of 3:36

An angle is two rays that share an endpoint.

That shared point is the vertex.

Read it: An angle at every vertex

An angle is made where two sides meet at a vertex. A hexagon has 6 vertices, so it has 6 angles.

Find a vertex, where two sides meet.
Go around the shape once, counting each vertex one time.
The number of vertices is the number of angles: 6.

Each angle is the opening between the two sides that meet at one vertex.

Every vertex has exactly one angle inside the shape, so vertices and angles match.

Going round once from a start you mark means no vertex is counted twice.

A flat shape has as many angles as vertices.

Counting the first vertex again at the end, and saying 7.

Mark where you start and stop when you reach it: the hexagon has 6 angles.

How many angles does a quadrilateral have? — 4. A quadrilateral has 4 vertices, so 4 angles.

Two rays sharing one vertex

Look around — corners are everywhere! In math, we call those corners angles. Let's build one from scratch.

Start with a single point. This will be the corner of our angle.

From that point, draw a straight line that keeps going forever in one direction. That's a ray.

Now draw a second ray from the very same point, going in a different direction.

The shared point where the two rays meet has a special name — the vertex.

And the two straight lines coming out of the vertex are the rays.

Look — the opening between the two rays, right here, is the angle.

Grade 4 · An angle is the shape made when two rays meet at a point

You see angles every day! The hands of a clock form an angle at the center.

An angle is the shape made by two rays that share one endpoint, called the vertex.

What you see

While they climb, your page writes one true line to ask about tonight, and a short note each Sunday.

MayaGrade 3 · Mathematics

Did you know?

A chessboard has 64 squares — share them out between the 8 rows and each row holds exactly 8.

Today’s goal: 1 star — one skill mastered, every rung of its ladder climbed
Climbing now: Divide within 100

An example student.

MayaGrade 3 · Mathematics

Maya earned 2 stars this week — Interpret multiplication as equal groups, which took 6 answers over 3 days before its star landed 3 days ago and Multiply by 6, 7, 8 and 9. Next up: Divide within 100.

An example week.

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Standards

CCSS.4.MD.C.5

Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint, and understand concepts of angle measurement

CCSS.4.MD.C.5a

An angle is measured with reference to a circle; an angle that turns through 1/360 of a circle is called a 'one-degree angle'

CCSS.4.MD.C.5b

An angle that turns through n one-degree angles is said to have an angle measure of n degrees

Grade 4

Quoted from the Common Core State Standards.

Where this sits

Comes after

Identify Shared Attributes of Shapes

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What a star here means

A star here is the top of a twenty-rung ladder, in four blocks of equal length — three of facts and one of the skill used in a real question — where a right answer climbs one rung and a wrong one drops back to the start of the block, never below it. The star is kept for good. How we grade

All of Grade 4

This is one rung of 71 in Grade 4 mathematics, in the order they build on each other.

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