- any of the four angles formed on the inside of two straight lines when crossed by a transversal
- the angle formed inside a polygon by two adjacent sides
See interior angle in American Heritage Dictionary 4
- Any of the four angles formed between two straight lines intersected by a third straight line.
- The angle formed inside a polygon by two adjacent sides.
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Angles 3, 4, 5, and 6 are interior angles; angles 3,6 and 4,5 are alternate interior angles.
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