When two lines are crossed by another line (which is called the Transversal), the pairs of angles:

• on one side of the transversal

• but inside the two lines

are called Consecutive Interior Angles.

d and f are Consecutive Interior Angles.

c and e are Consecutive Interior Angles.

When the two lines are parallel, any pair of Consecutive Interior Angles add to 180 degrees.

Play with it below (try dragging the points):

• on one side of the transversal

• but inside the two lines

are called Consecutive Interior Angles.

d and f are Consecutive Interior Angles.

c and e are Consecutive Interior Angles.

When the two lines are parallel, any pair of Consecutive Interior Angles add to 180 degrees.

Play with it below (try dragging the points):

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