Question
If one angle of a parallelogram is a right angle, then it is necessarily a _____________. (rectangle, square, rhombus).
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Answer
If one angle of a parallelogram is a right angle, then it is necessarily a rectangle. Explanation: 
We have, $\angle\text{A}=90^\circ$ In a parallelogram, opposite angles are equal. Therefore, $\angle\text{C}=90^\circ$ Similarly, $\angle\text{A}+\angle\text{D}=180^\circ$ $90^\circ+\angle\text{D}=180^\circ$ $\angle\text{D}=90^\circ$ Also, $\angle\text{B}=90^\circ$ Thus, a parallelogram with all the angles being right angle and opposite sides being equal is a rectangle.
We have, $\angle\text{A}=90^\circ$ In a parallelogram, opposite angles are equal. Therefore, $\angle\text{C}=90^\circ$ Similarly, $\angle\text{A}+\angle\text{D}=180^\circ$ $90^\circ+\angle\text{D}=180^\circ$ $\angle\text{D}=90^\circ$ Also, $\angle\text{B}=90^\circ$ Thus, a parallelogram with all the angles being right angle and opposite sides being equal is a rectangle.Need a full question paper?
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