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Parallelogram Consecutive Angles Theorem
See It in Action
Two examples of the idea done right—and one common look-alike that is not right.
EXAMPLE
EXAMPLE
NON-EXAMPLE
Statement:
In a parallelogram, each pair of consecutive angles is supplementary (their measures add up to 180°.
In simple terms:
Angles that are next to each other in a parallelogram always add up to 180°.
Example:
In parallelogram ABCD, ∠A + ∠B = 180°, ∠B + ∠C = 180°, and so on.
Why It Matters:
This helps in solving for unknown angles in parallelograms and in proving that a quadrilateral is a parallelogram.
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