Geometry Formulas

There are many geometry formulas you will use during your time studying geometry. GradeA presents clear graphics and explanations to help you understand all of these formulas..

Please select from the quick links below, or feel free to scroll through the page to look at all of the formulas.

Triangle:  A three sided figure.

Rectangle:  A quadrilateral with four right angles.

Parallelogram:  A quadrilateral with two pairs of opposite sides parallel.

Trapezoid:  A quadrilateral with exactly one pair of opposite sides parallel.

Circle:  A set of points all equidistant from a given point - the center.

Any Regular Polygon:  A figure with all sides and angles congruent.

Pythagorean Theorem:

The most common formula for right triangles is Pythagorean theoreamn. You probably have heard of this one before: a² + b² = c²

For more details, read visit our pythagorean theorem page, or visit our biography of pythagoras, the man credited with the discovery of the famous formula.

Trigonometry:

Many geometry students begin to learn the trigonometric functions towards the end of the course. You probably are only going to use the first three functions, sin, cos, and tan, but we listed all 6 just in case.

For a lot more details about trigonometry, visit GradeA's trigonometry page.

The formulas shown below are to be used on the coordinate plane.  The first point is given as (x₁, y₁) and the second point is (x₂, y₂).  For your problem, it does NOT matter which point you name "first" and which point you name "second."

If you did not find one of the formulas that you were looking for, please view these additional geometry formulas. You can download a .printable formula sheet that covers everything you will need to know in geometry