Consecutive interior angles is a useful tool. When 2 parallel lines are crossed (Transversal line) by another line, the pair of angles on one side of the transversal insides the 2 lines is called consecutive interior angles. These consecutive interior angles follow each other. Also consecutive interior angles add up to 180 degrees. This consecutive interior angles tool helps to prove that 2 lines crossed by transversal are parallel. We may say that consecutive interior angles are supplementary.
Example 1: A road crosses a set of railway tracks. The angle 3 is 70 degrees. Find angle 6 in the given figure.
=> Angle 2 and 6 are corresponding angles therefore A2 = A 6,
=> Angle 2 and 3 are vertical angles, therefore A2 = A3
=> Or we may say A3 = A 6 when we combine the above 2 statements
=> Now since A3 = 70 degrees
=> A3 = A 6 = 70 degree.
Example 2: A road crosses a set of railway tracks. The angle 1 is 110 degrees. Find angle 8 in the given figure.
In the given problem
=> Now since A1 = 110 degrees=> Angle 1 and 5 are corresponding angles
=> Therefore A1 = A 5
=> Angle 5 and 8 are vertical angles, therefore A 5 = A 8
=> Or we may say A 1 = A 8 when we combine
=> A 8 = 110 degrees