alternate angles

plural noun

, Geometry.

1. two nonadjacent angles made by the crossing of two lines by a third line, both angles being either interior or exterior, and being on opposite sides of the third line.

alternate angles

plural noun

1. two angles at opposite ends and on opposite sides of a transversal cutting two lines

alternate angles

1. Two angles formed on opposite sides of a line that crosses two other lines. The angles are both exterior or both interior, but not adjacent.

Word History and Origins

Origin of alternate angles¹

First recorded in 1650–60

Example Sentences

Frustules oblong or quadrate, adnate in filaments, attached by alternate angles and finally separating.

From Project Gutenberg

We may now state Prop. 16 thus:—If two straight lines which meet are cut by a transversal, their alternate angles are unequal.

From Project Gutenberg

And “if the lines are parallel, are alternate angles necessarily equal?”

From Project Gutenberg

That is to say, “If alternate angles are unequal, do the lines meet?”

From Project Gutenberg

If two straights make with a transversal equal alternate angles they have a common perpendicular.

From Project Gutenberg