A quadrilateral is a closed, flat, figure made of 4 straight sides.
All of these shapes are quadrilaterals.
Tip: “Quad” means “four”, and "lateral" means “sides”.
A quadrilateral is a 2-dimensional shape. This just means that it’s a flat shape.
Two-dimensional shapes have a width and height, but no depth.
Three-dimensional objects, like soccer balls, have an extra depth dimension.
Vertices are the points where two line segments meet.
Every quadrilateral has 4 vertices.
Tip: 'Vertices' is the plural of 'vertex'.
Quadrilaterals also have 4 angles.
The angles can either be acute, right, or obtuse.
An acute angle is less than 90 degrees.
A right angle is exactly 90 degrees.
An obtuse angle is more than 90 degrees but less than 180 degrees.
Here's an interesting fact to remember:
When you add up all the angles of a quadrilateral, you always get 360 degrees.
We see that there are 4 angles. If we add them all up, what will we get?
90° + 90° + 90° + 90° = 360°
Yes. The total is 360°.
There are three main types of quadrilaterals: parallelograms, trapezoids, and kites.
The opposite sides in a parallelogram are parallel to each other.
Sides A and C are opposite to each other. They're parallel lines.
B and D are also opposite sides and parallel to each other.
Tip: Parallel lines move toward the same direction, and their distance from each other is always the same. No matter how far we extend the lines, they will never meet at any point.
Let's look at 3 special types of parallelograms.
A rectangle is a parallelogram with 4 right angles. Some sides can be longer or shorter.
A square is a rectangle with 4 equal sides.
A rhombus has 4 equal sides, but its angles are not necessarily equal.
Two angles may be acute, and the other two angles may be obtuse.
A trapezoid has only one pair of parallel sides. It's not a parallelogram.
There are a few different kinds of trapezoids.
The trapezoid you see above is called an isosceles trapezoid.
An isosceles trapezoid has one pair of parallel sides.
The sides that are not parallel are equal. This means they have the same length.
Aside from the isosceles trapezoid, here are other examples of trapezoids:
An acute trapezoid has two acute angles on it's longer base side.
A right trapezoid has one right angle.
An obtuse trapezoid has one obtuse angle on each base.
A kite is a quadrilateral.
A kite has adjacent pairs of sides that are equal in length.
Sides J and K are adjacent and equal.
Sides L and M are also adjacent and equal.
Tip: Adjacent means "next to each other".
Quadrilaterals have 4 sides.
There are 3 kinds of quadrilaterals: parallelograms, trapezoids, and kites.
Parallelograms are quadrilaterals that have 2 pairs of parallel lines.
Every square, rhombus, and rectangle is a parallelogram.
Trapezoids have one pair of parallel lines.
A kite has 2 adjacent lines that are equal in length.
Great job learning about quadrilaterals. 👏
Now, complete the practice to help you remember for longer.