What makes two rays a pair of opposite rays?

Two rays form a pair of opposite rays if they share the same endpoint and extend in exactly opposite directions (180 degrees apart) along the same line. Together, they form a complete line.

Conditions

There are two rays.
They have the same starting point (endpoint).
Their directions are opposite along the same straight path.

Reasoning, step by step

Identify the common endpoint of the two rays.
Check that the rays extend in opposite directions from that endpoint.
Verify that they lie on the same line.
Conclude that they are opposite rays and their union is a line.

Example

The instructor shows $\overrightarrow{RT}$ and $\overrightarrow{RS}$ sharing endpoint R and pointing in opposite directions, stating they form the line through S, R, and T.

Common misconceptions

Thinking any two rays pointing in different directions are opposite rays.
Forgetting that opposite rays must share the exact same endpoint.

Watch the explanation

YouTubeGeometry Lesson 1 - Points, Lines, and Planes

4:09 – 4:45Watch this moment ↗

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.