Definition: Exterior, Interior, Alternate and Corresponding Angles
When a straight line intersects two other straight lines at two distinct points, between them are eight angles (see Fig.).
 Angles 1 and 2, 7 and 8 are called exterior angles;
 Angles 3 and 4, 5 and 6 are called interior angles;
 Angles 4 and 6, 3 and 5 are called alternate angles;
 Angles 1 and 5, 2 and 6, 3 and 8, 4 and 7 are called corresponding angles.
Mentioned in:
Propositions: 1 2
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References
Adapted from CC BYSA 3.0 Sources:
 Callahan, Daniel: "Euclidâ€™s 'Elements' Redux" 2014
Adapted from (Public Domain)
 Casey, John: "The First Six Books of the Elements of Euclid"