Angles in parallel lines

An introduction to alternate, corresponding and co-interior angles in parallel lines

Parallel lines are lines which are always the same distance apart and never meet. Arrowheads show lines are parallel.

Two parallel lines, intersected by another line

When a pair of parallel lines is cut with another line known as an intersecting transversal, it creates pairs of angles with special properties.

Corresponding angles

Corresponding angles are equal. The lines make an F shape. Notice that the F shape can be upside down or back to front.

Angles produced along a line, which is intersecting 2 parallel lines are identical

Alternate angles

Alternate angles are equal. The lines make a Z shape which can also be back to front.

Opposite angles on a set of parallel lines

Vertically opposite angles

Vertically opposite angles are equal.

Opposite angles produced by a line intersecting 2 parallel lines are identical
Question

Calculate the angles x and y. Give reasons for your answers.

3 angles produced by a line intersecting a set of parallel line are labelled 50 degrees, x and y

x is 50^\circ. Corresponding angles are equal.

y is 180 - 50 = 130^\circ. Angles on a straight line add up to 180°.