For example, the focal length formula (f=\frac{a}{4}) is used to calculate the distance from the focal point to the directrix, where (a) is the parameter of a parabola. There is also a tangent slope formula (y=2ax+b), which is used to calculate the tangent slope of a point on the parabola, where (a) and (b) represent the parameters and intercept of the parabola respectively.