Calculate internal angles between parallel lines cut by a transversal.
Interior Angle
°
Geometric Relations
75°
Alternate Interior
Consecutive Interior105°
Vertical Angle75°
Supplementary105°
About this calculator
The Z-Pattern
Alternate interior angles are a pair of angles on opposite sides of the transversal and between the two parallel lines. They form a distinctive 'Z' or 'S' shape. When the lines are parallel, these internal angles are exactly equal.
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Pro Tips
Consecutive interior angles (on the same side) sum to 180°.
Look for the 'Z' shape—the angles in the corners of the 'Z' are the alternate interior pair.
This property is only true if the two main lines are perfectly parallel.
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Fun Facts
"This theorem is essential in mechanical engineering to ensure shafts and axles remain parallel."
"The term 'transversal' comes from Latin 'trans-versalis', meaning 'crossing'."
"Artists use these principles in linear perspective to create the illusion of depth."
