Definition:Transversal (Geometry)/Alternate Angles

Definition

Alternate angles are interior angles of a transversal which are on opposite sides and different lines.

In the above figure, the pairs of alternate angles with respect to the transversal $EF$ are:

$\angle AHJ$ and $\angle DJH$

$\angle CJH$ and $\angle BHJ$

Also known as

It may be possible to see the alternate angles of a transversal referred to as the alternate interior angles.

However, most sources take it for granted that the angles in question are interior.

Also see

• Equal Alternate Angles implies Parallel Lines
• Parallelism implies Equal Alternate Angles

• Definition:Interior Angle of Transversal
• Definition:Exterior Angle of Transversal
• Definition:Corresponding Angles of Transversal

• Results about transversals in the context of geometry can be found here.

Sources

• 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): alternate angles
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): alternate angles
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): transversal
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): alternate angles
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): transversal
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): alternate angles
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): transversal
• 2021: Richard Earl and James Nicholson: The Concise Oxford Dictionary of Mathematics (6th ed.) ... (previous) ... (next): alternate angles