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Opposite sides of a parallelogram are equal. So ab = dc and ad = bc. But you are also told that ab = bc. So all four sides are equal.

Opposite angles of a parallelogram are equal. So abc =90 degrees implies that cda is 90 degrees. The remaining two angles add up to 360 - (abc + cda) = 180 degrees and both are equal. So they, too , must be 90 degrees each. So all four angles are equal.

A parallelogram with four equal sides and four equal angles is called a square.

Q: Abcd is a parallelogram ab equals bc and angle abc equals 90 degree explain why abcd is a square?

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Square rectangle rhombus parallelogram

...There is no such thing. It would be a square. It's a square. -____- at the person before me.

No, a parallelogram is not always a square, but a square is a parallelogram.

Square = parallelogram and a square trapezoid = trapezoid Parallelogram = Parallelogram

No, a parallelogram is not necessarily square.However, by definition, a square is always a parallelogram.

Related questions

Since a parallelogram has two sets of parallel sides, a parallelogram containing a 90 degree angle would precisely resemble a square.

A square is a parallelogram with 4 equal sides and 4 90 degree angles.

A square is a parallelogram because it has two sets of parallel sides. It's a rhombus because every side is the same length.

Square rectangle rhombus parallelogram

...There is no such thing. It would be a square. It's a square. -____- at the person before me.

No, a parallelogram is not always a square, but a square is a parallelogram.

No, a parallelogram is not always a square, but a square is a parallelogram.

Area of a parallelogram is base*height 15*7=105 105 square centimeters

Square = parallelogram and a square trapezoid = trapezoid Parallelogram = Parallelogram

Because it is a 4 sided quadrilateral with with 2 pairs of parallel sides

A square is always a parallelogram. Every square is a parallelogram.

No, a parallelogram is not necessarily square.However, by definition, a square is always a parallelogram.