In analytic geometry, also known as coordinate geometry, we think about geometric objects on the coordinate plane. For example, we can see that opposite sides of a parallelogram are parallel by by writing a linear equation for each side and seeing that the slopes are the same.
You probably know what parallel and perpendicular lines are. In this tutorial, you will learn how these relationships are expressed on the coordinate plane (spoiler: parallel lines have the same slope, and the product of the slopes of perpendicular lines is always -1).
You know that a circle can be viewed as the set of all points that whose distance from the center is equal to the radius. In this tutorial, we use this information and the Pythagorean Theorem to derive the equation of a circle.