# Basic Geometry

#### Basic Shapes & Angles

This is where it all begins: basic shapes, lines, and angles.
Read on and let us take you on a magical geometry tour...
NameDescriptionExamplePointA single location.Usually drawn as a dot.It...

#### Angles

Not to be confused with angels, angles are the pointed corners of shapes. Angles can be named three different ways. This angle could be named any of these ways: (counterclockwise) (cl...

#### Parallel Lines & Transversals

A transversal is a line that intersects two or more other lines. When it intersects parallel lines, many angles are congruent. Let's take a peek at what this means. Lines k and j are parallel....

#### Polygons

A polygon is any closed figure with three or more straight sides. "Closed" means that there are no gaping holes in it and that all sides connect together.
These Are Polygons:These Are Not Poly...

#### Triangles

Triangles are three sided polygons, but we're sure that you already knew that. The triangle is the most sturdy of polygons. Its strong shape has been used to build buildings and bridges since...

#### Quadrilaterals

Quadrilaterals are four sided shapes. The most common include squares and rectangles, but there are loads of others as well. Like triangles, they are classified by their angles and sides. In t...

#### Angles in a Polygon

As we discussed before, the three
angles of a triangle always add up to 180°.In each case
. By the way, means
"the measurement of angle A".To find the total number of degrees
in...

#### Circles

A circle is the set of all points equal in distance from a center point. If you pinned a piece of yarn down, then tied a pencil to the other end of the yarn and pulled the pencil around, you'd r...

#### Similar Figures

Similar figures have the same shape, but might not be the same size. When two shapes are similar, their corresponding sides are proportional (see ratios and proportions) and their correspon...

#### Perimeter & Circumference

The perimeter of a shape is the distance around the outside of the figure. It's pretty simple; just add up the lengths of each side. Perimeter is often used to find the measurements needed to pu...

#### Area (Polygon, Triangle, Circle, Square)

Area is the amount of space inside a two-dimensional shape. If you think about the floor of your bedroom, the area would be the maximum amount of floor you could throw your stuff on before you c...

#### Area Formulas

Let's go over these formulas one more time.Formulas for different shapes:Area of Rectangle = Base x HeightArea of Triangle = ½(Base × Height)Area of Parallelogram = Base × HeightArea of Trape...

#### Area of Irregular Shapes

In real life figures are often irregular shapes - a little bit messy. Think of your messy bedroom once more ‐ is it a perfect rectangle? The trick: break these figures into shapes that you kno...

#### 3D Objects (Prisms, Cylinders, Cones, Spheres)

Three‐dimensional objects are the solid shapes you see every day, like boxes, balls, coffee cups, and cans.
Here are some helpful vocabulary terms for solids: Base: the bottom surface of...

#### Volume of Prisms & Cylinders

The volume of a solid is the amount of space inside the object. It's how much water fits inside a bathtub, how much sand fills a bucket, or how much soda your friend can chug and hold in his sto...

#### Volume of Pyramids & Cones

The formula for the volume of pyramids and cones tells you how much space is inside each object.For these two solid shapes, the volume formula is the same: it's one third of the area of the...

#### Volume of Spheres

To find the volume of a sphere, follow this simple formula (which took a brilliant ancient Greek mathematician named Archimedes years to derive):Volume of a Sphere = 4/3π x radius cubed = 4/3πr3

#### Surface Area

The surface area of a solid is the area of each surface added together. There are few formulas to memorize (w00t!). The keys to success: make sure that you don't forget a surface and that you have...

#### Pythagorean Theorem

A long time ago, in ancient Greece, a brilliant guy named Pythagoras discovered something pretty amazing and useful.
Pythagorean Theorem: a2 + b2 = c2In a right triangle the sum of the squ...