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Question Video: Identifying the Measure of an Angle Mathematics

If the line 𝐴𝐶 is a straight line, find the measure of ∠𝐴𝐵𝐶.


Video Transcript

If the line passing through 𝐴 and 𝐶 is a straight line, find the measure of angle 𝐴𝐵𝐶.

In this question, we are asked to find the measure of an angle that lies on a given straight line. The easiest way to answer this question is to recall that the measure of a straight angle, that is, an angle whose sides form a straight line, is 180 degrees. This is enough to answer the question. However, it can be useful to understand why this angle is said to have measure 180 degrees.

To do this, we recall that an angle is a rotation between two rays that share a starting point. And we define the measure of a full turn to be 360 degrees. If we were to only perform half a turn, then the sides would form a straight line. We would need to half the angle measure to get 180 degrees. Hence, the measure of angle 𝐴𝐵𝐶 is 180 degrees.

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