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### Course: Class 8 (Old)>Unit 3

There are many different types of quadrilaterals. A quadrilateral is defined as a two-dimensional shape with four sides, four vertices, and four angles. There are two main types: concave and convex. There are also various subcategories of convex quadrilaterals, such as trapezoids, parallelograms, rectangles, rhombi, and squares. Created by Sal Khan.

## Want to join the conversation?

• Can someone give me an overview of the differences between Rhombi, Parallelograms and Rectangles?
• So you start with a parallelogram, two pairs of parallel sides, opposite sides are congruent, adjacent angles are supplementary, diagonals bisect each other, and opposite angles are congruent.
IF a parallelogram has an angle of 90 degrees (thus all 4 angles are 90) it is a rectangle - all rules of parallelograms apply plus diagonals are congruent.
IF a parallelogram has 4 equal sides, then it is a rhombus. All parallelogram rules apply plus the diagonals are perpendicular bisectors of each other.
IF it has both equal sides and all 90 degree angles, then it is a square which has all the properties of parallelograms, rhombii, and rectangles.
• It is and do quadrilaterals have to be closed?
• Yes, they have to be closed. In fact, all polygons have to be closed.
• what is the formula to find the area of a diamond ??????????
• The area formula for a Rhombus is:

A = (1/2) (d1) (d2)

d1 & d2 represent the length of the 2 diagonals
• I do not understand the difference between a quadrilateral, parallelogram, rhombus?
• the rhombus is a slanted square and the parallelogram is a slanted rectangle. they both are quadrilateral. The term 'quadrilateral' means 4 sides. so a square, rhombus etc. are quadrilaterals. Hope this helps! :)
• Does the sides have to be equal to be a quad.
• not necessarily. the weird pink shape that he showed did not have equal sides
• How does a square go under the description of both the rectangle and rhombus? Is it because a square and a rectangle and rhombus all have 2 parallel sides? or is it because of something else?
• A rectangle has 4 straight sides and 4 right angles.

A rhombus must have opposite equal angles and 4 equal sides.

A square has 2 sets of opposite right angles and 4 straight, equal sides, so it fits into both categories.

Hope this helps!
• ¿Could a Perfect Hexagon be a parallelogram?
• Even though you may think there is another parallel side for each side in a regular hexagon, the definition of a parallelogram is a four-sided plane rectilinear figure with opposite sides parallel.

I hope this helped!
• If a square can be a rectangle, can it be a rhombus?
• Yes. All squares are both rectangles and rhombi.
• It is and do quadrilaterals have to be closed?
• Yes, all polygons are defined as closed figures.
• Why would people think that trapezoids have to have only one pair of parallel sides? If they were right, what would happen to the hierarchy of quadrilaterals