# 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.
Origin of alternate angles
1650-1660
1650-60
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for alternate angles
Historical Examples
• Euclid introduced the subject by the proposition that, if alternate angles are equal, the lines are parallel.

David Eugene Smith
• And “if the lines are parallel, are alternate angles necessarily equal?”

• The sides of the octagon are equal, and the alternate angles coincident.

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

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

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

Charles Sumner Boyer
British Dictionary definitions for alternate angles

## alternate angles

plural noun
1.
two angles at opposite ends and on opposite sides of a transversal cutting two lines
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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alternate angles in Science
 alternate angles   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.
The American Heritage® Science Dictionary
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### Difficulty index for alternate angles

Few English speakers likely know this word

### Word Value for alternate

9
11
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