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

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 ...

VIDEO 5:07 minutes

### 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.

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

### Proof: Opposite sides of parallelogram congruent

VIDEO 8:30 minutes
Proving that a figure is a parallelogram if and only if opposite sides are congruent

### Proof: Diagonals of a parallelogram bisect each other

VIDEO 9:06 minutes
Proving that a quadrilateral is a parallelogram if and only if its diagonals bisect each other

### Proof: Opposite angles of parallelogram congruent

VIDEO 4:08 minutes
Showing that opposite angles of a parallelogram are congruent

PRACTICE PROBLEMS

### Proof: Rhombus diagonals are perpendicular bisectors

VIDEO 4:04 minutes
Proving that the diagonals of a rhombus are perpendicular

### Proof: Rhombus area half product of diagonal length

VIDEO 5:07 minutes
Showing 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