Angles in a Triangle
11+ Maths, topic 1.5.1
Angles in a Triangle
The angles in a triangle add up to 180°. You can use this information to solve triangle problems.
Find the missing angle
The angles in a triangle add to 180°
- So you need to subtract the sum of the given angles from 180 degrees to work out the missing angle.
Work out the sum of given angles
- You have been given the top angle - 45°.
- We know that the other angle is a right angle by looking at it - that means it is 90°.
The sum of the given angles
- 90 + 45 = 135°.
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Working out the missing angle
- So the missing angle is 180 - 135.
- The missing angle is 45°.
Test yourself on Angles in a Triangle
What do the angles in a triangle add up to?