Distance in the Coordinate PlaneDistance = if you’re measuring the distance between the points (x1, y1) and (x2, y2). Distance in the Coordinate Space DistanceDistance = if you’re measuring the distance between the points (x1, y1, z1) and (x2, y2, z2). Midpoint between Two PointsMidpoint = , where the endpoints of a line segment are (x1, y1) and (x2, y2). Point-Slope Form of the Equation of a Liney – y1 = m(x – x1), where m is the slope of the line, and (x1, y1) is a point on the line. Slope-Intercept Form of the Equation of a Liney = mx + b, where m is the slope of the line, and b is the y-intercept of the line. Both m and b are constants. Slope of a LineSlope = , where two points on the line are (x1, y1) and (x2, y2). Standard Form of the Equation of a Circle(x – h)2 + (y – k)2 = r2, where (h, k) is the center of the circle, and r is the radius. When centered at the origin, the equation simplifies to x2 + y2 = r2. Standard Form of the Equation of a Parabolay = a(x – h)2 + k, where a, h, and k are constants.