How to Solve Angles of Parallel Lines & Transversals

The definition of parallel lines is they could travel for infinity in both directions and never cross each other. A transversal is a line that crosses both of the parallel lines. Though the transversal intersects the parallel lines at different points, it has the same effect on the lines by creating the same angles for both intersections.

• 1

  Place the protractor along the top parallel line where the transversal intersects.

• 2

  Measure the larger of the two angles on the top. Write down the measurement.

• 3

  Subtract that angle from 180, since a line represents a 180-degree angle. The result is the other top angle. Write down the second measurement.

• 4

  Write down the original measurement in the angle right across from it in the intersection. When two lines intersect, the opposing angles mirror each other. Write down the measurement of the second angle in the angle opposite it.

• 5

  Copy the measurement angles to the intersection of the other parallel line and the transversal in the exact same way. When a transversal intersects parallel lines, it creates the same angles at each intersection.

• 6

  Compare the angles. The top-right and lower-left angles of both intersections should measure the same. The lower-right and top-left angles of both intersections should also measure the same.