Two straight lines, which exist in a plane, are intersected by a straight line, which is called as a transversal line. This transversal line creates total 8 angles on these two lines and each line has 4 angle like a traversal line XY, which intersect two lines ‘AB’ and ‘DE’ and creates 8 angles.
Angles on straight line
AB: $\angle$i, $\angle$j, $\angle$k, $\angle$l
Angles on Straight Line
DE: $\angle$m, $\angle$n, $\angle$o, $\angle$p
When two angles from opposite groups opposite in same side of traversal, then both angle pair are known as an Consecutive Exterior Angles.
i and $\angle$p, $\angle$j and $\angle$o are Consecutive Interior Angles
We use following steps for evaluation of consecutive exterior angles:
First we calculate first consecutive exterior angle from any of two consecutive interior angles.
Now it’s easy to find out other consecutive exterior angle from given transversal line by using following rule.
Consecutive Exterior Angle 2 = 180 - Consecutive Exterior Angle 1
Suppose we have to find consecutive exterior angle of a transversal line, whose first consecutive exterior angle is equal to 60 degree. The other consecutive exterior angle is,
Consecutive Exterior Angle 2
= 180 - Consecutive Exterior Angle 1
= 180 - 60
So, the other consecutive exterior angle of given transversal line is equal to ‘120 degree’.