How do you name a ray?

Conditions

• The object being named is a ray.
• Two points are available: the endpoint and a direction point.

Reasoning, step by step

1. Identify the endpoint of the ray (e.g., X).
2. Identify a second point on the ray in the direction of extension (e.g., R).
3. Write the letters in order: endpoint first, then direction point (XR).
4. Place a right-pointing arrow above the letters to get $\overrightarrow{XR}$.
5. Note that even if the ray is drawn pointing left or down, the notation arrow still points right.

Example

The instructor names a ray starting at X and going through R as $\overrightarrow{XR}$, and a leftward ray starting at E and going through F as $\overrightarrow{EF}$.

Common misconceptions

• Writing the direction point before the endpoint.
• Thinking the arrow in the notation must point in the same physical direction as the drawn ray.

Watch the explanation

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