Find a missing adjacent angle
The idea
Identify the total angle: a right angle is 90° and a straight angle is 180°.
Step by step
- Identify the total angle: a right angle is 90° and a straight angle is 180°.
- Add adjacent parts to make the total; subtract the known part to find the missing part.
- Check that both positive parts add back to the labeled total.
Example
An angle of 90° is split into two adjacent angles. One is 35°. What is the other angle in degrees?
Answer
55
The two parts add to 90°. 90 − 35 = 55°.
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Draw a right angle and split it with a ray. Choose a measure for one part and find the other.
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