Question

In a parallelogram ABCD, angle A = 90degree. (i) What is the measure of angle B? (ii) Write a special name of the parallelogram.

Answer 1

We know that sum of adjacent angles of a parallelogram is 180°

∴ ∠A + ∠B = 180°

90 + ∠B = 180°    [∵ ∠A = 90° given]

∴ ∠B = 90°

Also,

∠A = ∠C = 90°  [Opposite angles of parallelogram are equal]

∠B = ∠D = 90°

Since all interior angles of parallelogram ABCD are of 90°, we can say it is a Rectangle.

(opposite sides are equal and parallel and each interior angle is of 90°)