What is a Parallelogram Special Cases of Parallelogram Dont Memorise

Here's another type of quadrilateral. Let's name it ABCD. In this quadrilateral, both pairs of opposite sides are parallel. The first pair of opposite sides is AB and DC. We can see that AB is parallel to DC. We use two arrows in the same direction to show that the sides are parallel. The second pair of opposite sides is AD and BC. We can also see that AD is parallel to BC. So we draw arrows like this. Such quadrilaterals are called parallelograms. Both pairs of opposite sides are parallel. This was the basic property of parallelogram. In parallelogram, the opposite sides are also equal. This side will be equal to this side. We can say that AB is equal to DC. This side will be equal to this side. AD is equal to BC And guess what, in parallelogram, the opposite angles are also equal. Opposite angles are angles which do not have common side. This angle will be equal to this angle. Angle DAB is equal to angle DCB. And this angle will be equal to this angle. Angle ABC is equal to angle ADC. Remember, this is the basic property of parallelogram. The opposite sides as well as the opposite angles are equal. Let's see special case of parallelogram. In this parallelogram, all the sides are equal to each other. This is rhombus. So rhombus is parallelogram with all its sides equal. It will have all the properties of parallelogram, as well as this additional property that all its sites will be equal. There is another special case of parallelogram. Let me draw it on new page. Remember, the opposite sides have to be parallel. It is quadrilateral drawn like this. The opposite sides of this quadrilateral are parallel. So it is parallelogram. Let's name the quadrilateral ABCD. Why is it special? All the angles in the quadrilaterals are right angles. This special case of parallelogram is called rectangle. This is how rectangle can be defined. It is parallelogram with all angles being right angles. Just like in parallelogram the opposite sides of rectangle are equal. This side will be equal to this side, and this side will be equal to this one. Now it gets even more interesting. This quadrilateral is special case of rectangle. Let's call it PQRS. Like the rectangle, all its angles are right angles, but it has an additional property. All Its sides are equal to each other. This type of quadrilateral is called square. Basically, it is rectangle with all its sides equal. The rectangle is the special case of the parallelogram. And this square is special case of rectangle. But wait, square the opposite sides are parallel. So it is parallelogram. All Its sides are also equal, so it's also rhombus. Again, what is rhombus It is quadrilateral with all its sides equal and opposite sides parallel to each other. But how is the square different from normal rhombus? It is rhombus in which all angles are right angles. Next, we will review all the types of quadrilaterals, and how they are related to each other.