Lines, Line Segments, and Rays

Do you know what geometry is?

**Geometry **is the math of shapes and spaces.

😃 In** geometry**, we work with different kinds of shapes.

(Can you name each of these shapes? Try it! 🤗)

In geometry, we also work with more simple things like** points, lines, line segments, **and **rays**.** **

These are the **building blocks**** **of geometry. 😺

In this lesson, let's learn about each of them. 😎

🤓 Look at these dots.

Each of these dots is called a **point**.

Apointis any location in space. It hasno length, height or width.

👉 Points are labelled with** single, capital letters**.

For example, this is Point A.

👉 The tip of a pencil can be thought of as a point.

👉 Each location on a shape is a point.

😃 Look at this picture. It shows a horizon.

Can you tell where a horizon ends on both sides? 🤔

No we can't. 🤓

This is because **a horizon keeps going **on both sides. It never ends. It's called a **line**.

Alineis a straight path of points that keeps going in both directions forever.

In geometry, a line is drawn with arrows on both ends.

Do you think we can measure the length of a line? 🤔

No! 😁 We can't.

✅ Since a line never ends, we **cannot measure its length**.

👉** To name a line,** use any two points on it.

For example, to name this line, we use two points on it, A and B, and call it **Line AB or Line BA.**

When writing the name, put a **two-sided arrow on top **of the label.

🤓 Look at the edges of this chessboard.

Each edge is a **line segment**.

A line segment is a straight path with two endpoints.

A line segment is drawn with points on either end.

Can you measure the length of a line segment? 🤔

Yes! You can! 🤗

✅ This is because, at a certain point, **a line segment ends**.

👉** To name a line segment**, use its endpoints.

For example, this line segment can be called **Line segment AB or Line segment BA**.

When writing the name, put **a line on top **of the label.

Look at these rays of light. 🌞

We know where the rays start.

But can you tell where these rays end? 🤔

No! We can't.

This is because a ray starts at a point and keeps going the other way forever.

Arayis a straight path of points that starts at one point, and keeps on going in one direction forever.

✅ A ray has one endpoint.

A ray is drawn with a point on one end, and an arrow on the other end.

Can you measure the length of a ray? 🤔

No! 😎 You can't.

✅ This is because a ray, like a line, **never ends.**

👉** To name a ray**, start from its endpoint, and end at any point on the other side.

**✅ Remember! **There is **only one way to name a ray**, which is starting from its endpoint.

For example, this ray can be called **Ray XY (but not Ray YX).**

When writing the name, put a **one-sided arrow on top **of the label.

Congratulations! 👏 You now know what lines, line segments and rays are. Start your practice below.

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