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Question
Can a quadrilateral ABCD be a parallelogram if ∠D + ∠B = 180°?
Solution
For ∠D + ∠B = 180°, quadrilateral ABCD may or may not be a parallelogram. Along with this condition, the following conditions should also be fulfilled.
The sum of the measures of adjacent angles should be 180º.
Opposite angles should also be of same measures.
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