Question

What are alternate interior angles?

Answer 1

Hint: For solving this question you should know what are the alternate interior angles and how are they formed in any diagram. The angles which are formed inside two parallel lines, when intersected by a transversal are always equal to its alternate pairs. These angles are called alternate interior angles.

Complete step by step solution:
According to our question, we have to explain the alternate interior angles. The alternate interior angles are the angles which are formed when a transversal intersects two coplanar lines. They always lie on the inner side of the parallel lines but on the opposite side of the transversal. The transversal crosses two lines which are coplanar at separate points. These angles represent where the two given lines are parallel to each other or not. If the angles are equal to each other then the lines crossed by the transversal are parallel. According to the figure given below,

We can see two parallel lines are intersected by a transversal. Therefore, the alternate angles inside the parallel lines will be equal. That is,
$\angle A=\angle D$ and $\angle B=\angle C$
By this figure we can say that the angles formed on the same side of the transversal which are inside the two parallel lines is always equal to ${{180}^{\circ }}$. If the lines are not parallel then the pair of angles will not be equal.
Thus, we have explained the alternate interior angles.

Note: If we see then it is clear that the lines are always parallel to each other. Then it becomes the interior angles. But if these are not parallel then it will not be interior angles who are equal to each other. Thus, we can also find in any question if the lines are parallel or not.