This equation computes the Resistance `R_1` (see diagram) of the unity gain low pass filter implementation of the Sallen-Key topology. This electronic filter is a special case of a second-order unity gain filter version of the voltage-controlled voltage-source (VCVS) topology.
`R_1` is a function of the Resistance, `R_2`, and Capacitances (`C_1`, `C_2`) shown in the diagram.
