Alternate interior and exterior angles — lesson. Mathematics State Board, Class 7.

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Alternate interior angles:

The region between the two lines

$m$ and

$n$ are known as interior regions and the located in this region called interior angles.

Now observe the above diagram, there each of pair of angles named

$∠a$ and

$∠b$ ,

$∠c$ and

$∠d$ are marked on the opposite side of the transversal line

$l$ and are lying between lines

$m$ and

$n$ are called alternate interior angles.

The each pair of alternate interior angles are equal, only when a transversal cuts the two parallel lines.

Alternate Exterior angles:

In the above diagram, we can notice each pair of angles named

$∠1$ and

$∠7$ ,

$∠2$ and

$∠8$ are marked on the opposite side of the transversal line

$l$ and are lying outside of the lines

$m$ and

$n$ are called alternate exterior angles.

The each pair of alternate exterior angles are equal, only when a transversal cuts the two parallel lines.

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4. Alternate interior and exterior angles