Question

Identify the pair(s) of co-interior angles for the following figure:


Here the inclined lines are parallel to each other.

• A. $\angle d$ and $\angle f$
• B. $\angle d$ and $\angle j$
• C. $\angle c$ and $\angle i$
• D. $\angle e$ and $\angle h$

Answer 1

Answer: (A), (B), (C)

$\angle c$ and $\angle i$

The angles that lie inside the two parallel lines and on the same side of the transversal are called co-interior angles.


In the given figure, the black line is the transversal, whereas the pairs of parallel lines are $\{green,blue\},\{green,violet\}$ and $\{blue,violet\}.$

The pair of co-interior angles $\angle d$ and $\angle f$ is associated with the green and blue parallel line pair.

Similarly, the pairs of co-interior angles $\angle d,\angle j$ and $\angle c,\angle i$ are associated with the green and violet parallel line pair.

However, $\{\angle e,\angle h\}$ is not pair of co-interior angles of any of the parallel line pairs, these are vertically opposite angles.