# Quadrilaterals

12 videos

2 skills

Not all things with four sides have to be squares or rectangles! We will now broaden our understanding of quadrilaterals.

### Quadrilateral overview

VIDEO
8:24 minutes

"Quad" means "four" and "lateral" means "line." A quadrilateral is literally a shape with four sides (lines) and four angles. Let's learn the difference between concave and convex quadrilaterals as well as trapezoids, parallelograms, and ...

### Quadrilateral properties

VIDEO
5:07 minutes

How about this: we are given a 4-sided shape and asked to determine whether its properties qualify it to be called a quadrilateral (or category of quadrilaterals). Check it out.

### Quadrilaterals: kites as a geometric shape

VIDEO
5:38 minutes

Is a kite a quadrilateral? Is it a rhombus? A parallelogram? Let's find out.

### Quadrilaterals: find the type exercise

VIDEO
2:49 minutes

Take a look at the given data and determine what type of quadrilateral we have.

### Quadrilateral types

PRACTICE PROBLEMS

Identify quadrilaterals based on pictures or attributes. Quadrilaterals included are parallelograms, rhombuses, rectangles, and squares.

### Proof: Opposite sides of a parallelogram are congruent (and conversely)

VIDEO
8:30 minutes

Sal proves that a figure is a parallelogram if and only if opposite sides are congruent.

### Proof: The diagonals of a parallelogram bisect each other (and conversely)

VIDEO
9:06 minutes

Sal proves that a quadrilateral is a parallelogram if and only if its diagonals bisect each other.

### Proof: Opposite angles of parallelogram are congruent

VIDEO
4:08 minutes

Sal proves that opposite angles of a parallelogram are congruent.

### Quadrilateral angles

PRACTICE PROBLEMS

### Proof: Rhombus diagonals are perpendicular bisectors of each other

VIDEO
4:04 minutes

Sal proves that the diagonals of a rhombus are perpendicular, and that they intersect at the midpoints of both.

### Proof: Rhombus area is half the product of the lengths of its diagonals

VIDEO
5:07 minutes

Sal proves that we can find the area of a rhombus by taking half the product of the lengths of the diagonals.

### Area of a parallelogram

VIDEO
5:42 minutes

Guess what's interesting about the opposite sides of a parallelogram? That's right....they are parallel! Let's find the area--base times height

### Whether a special quadrilateral can exist

VIDEO
5:08 minutes

Proving whether a special quadrilateral can exist

### Rhombus diagonals

VIDEO
4:38 minutes

Proof that the diagonals of a rhombus are perpendicular bisectors of each other