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## Basic geometry and measurement

### Course: Basic geometry and measurement > Unit 4

Lesson 1: Quadrilaterals introduction# Identifying quadrilaterals

Classify quadrilaterals, including rectangles, rhombuses, and squares.

## Quadrilaterals

A quadrilateral is a polygon with four sides.

### Study some examples

Here are some examples of quadrilaterals:

### Try it yourself

## Special types of quadrilaterals

Some quadrilaterals go by special names like

*rectangle*,*rhombus*, and*square*. Let's learn about them!## Rectangles

What makes a shape a rectangle?

- There are four right angles.
- There are four sides because it's a quadrilateral.

### Study some examples

Here are some examples of rectangles:

### Try it yourself

### Challenge problem

Let's consider one more shape:

## Rhombuses

What makes a shape a rhombus?

- All sides are the same length.
- There are four sides because it is a quadrilateral.

### Study some examples

Here are some examples of rhombuses:

### Try it yourself

## Squares

What makes a shape a square?

- All sides are of equal length.
- There are four right angles.
- There are four sides because it's a quadrilateral.

### Study some examples

Here are some examples of squares:

### Try it yourself

## Challenge question 1

## Challenge question 2

## Want to join the conversation?

- why is a square rectangle?(161 votes)
- A rectangle is a specific type of quadrilateral, and a square is a specific type of rectangle so you can think of a square as a subset of a subset, also you can think of a square as a rectangle and a rhombus combined(61 votes)

- why is sqare special shape?(19 votes)
- A square is the type of quadrilateral (four-sided figure) with the most properties. A square has four equal sides and four right (90-degree) angles. These two properties lead to more properties.

A square’s two diagonals are equal in length.

A square’s two diagonals form a right (90-degree) angle at the point where they cross each other.

A square’s two diagonals divide each other into two equal segments.

A square’s two diagonals divide each of the square’s four right (90-degree) angles into two equal 45-degree angles.

Opposite sides of a square are parallel.

A square has the most lines of symmetry (four), of all quadrilaterals.

Have a blessed, wonderful day!(14 votes)

- Is a heart a type of circle?(10 votes)
- No.

A circle has 1 side and infinite lines of symmetry.

A heart doesn't have either of those.(27 votes)

- what is fraction(6 votes)
- A fraction is a part of a whole of equally divided parts. For example, if you have 1/2 as a fraction, this means you would have two equal parts of a whole. The numerator(top) shows how many parts there are while the denominator(bottom) shows how many equal parts would make a whole. Hope this was helpful. :)(28 votes)

- How does one calculate the perpendicular bisect of a certain line?(11 votes)
- You calculate the bisect by the rectangular height of the square(4 votes)

- Square has all equal side lengths and rectangl has 2 short and 2 big side lengths, and Howcome square is a rectangle?(12 votes)
- They both have 4 sides(7 votes)

- How many shapes are there in the world?(3 votes)
- I would have to guess that the number of shapes in the world cannot be counted accurately because there are so many.

I'm not suggesting that you do it, but imagine cutting down EVERY tree in the world. You would find that every tree trunk has a different shape than all the others. Every snow flake apparently is a different shape than all the others. Every cloud has a different shape, every leaf has a different shape, every stream has a different shape. Etc.

There are just too many to count.(20 votes)

- Is there a group for things without paralel sides. I hope there is. and if there isn't a group that is pure weird because every quadrilateral should have a group. The square is so lucky because it is every group(11 votes)
- Those are mostly classified by the number of sides they have so if you had a 4 sided shape with no parallel sides it's just called a quadrilateral.(7 votes)

- I was curious why a square is a rectangle as well but I have the answer now.(13 votes)
- Why is a square a rectangle?On test it's wronge(10 votes)
- A square is a rectangle because it meets the definition of one - a parallelogram (a quadrilateral with opposite sides parallel) with a right angle (square) in each corner. So, think about it, a square has 4 sides, opposite sides are parallel, and each corner has a right angle/square, therefore it is also a rectangle but not all rectangles are squares. Good luck in the future, hope this helps.(9 votes)