Angles on a line and round a point · Year 8
In Year 8 you learn: giving reasons in angle problems.
Angles that sit together on a straight line make a half turn, and angles that meet at a point make a full turn. When two straight lines cross, the opposite angles are equal. These three facts solve a huge number of angle problems.
Key facts
- Angles on a straight line add up to 180°.
- Vertically opposite angles (opposite each other where two lines cross) are equal.
- Neighbouring angles where two lines cross add up to 180°.
- For algebra questions, write an equation from one of these facts and solve it.
Worked examples
Example 1
Two straight lines cross. One angle is 48°. Find the other three angles.
Answer: 48°, 132° and 132°