Angles in parallel lines · Year 7
In Year 7 you learn: corresponding and alternate angles.
When a straight line (a transversal) crosses two parallel lines, it makes the same angles at each crossing. Corresponding, alternate and co-interior angles let you move angles from one crossing to the other.
Key facts
- Corresponding angles (F shape) are equal.
- Alternate angles (Z shape) are equal.
- At each crossing, vertically opposite angles are equal and neighbouring angles add to 180°.
- Arrows on lines show that they are parallel.
Worked examples
Example 1
The two lines are parallel. Find the angle x.
Answer: x = 62°
Example 2
The lines are parallel. The marked angles are (3x + 15)° and (5x − 25)°. Find x and the size of the angles.
Answer: x = 20; both angles are 75°
Example 3
The two horizontal lines are parallel. Find the angle x at the bend.
Answer: x = 75°