1-7 The symbol for resonant frequency used in this text is f. Different texts and references may use other symbols for resonant frequency, such as f_{o}, F_{r}, and fR. The symbols for many circuit parameters have been standardized while others have been left to the discretion of the writer. When you study, apply the rules given by the writer of the text or reference; by doing so, you should have no trouble with nonstandard symbols and designations. The resonant frequency formula in this text is: By substituting the constant .159 for the quantity the formula can be simplified to the following: Let's use this formula to figure the resonant frequency (f_{r}). The circuit is shown in the practice tank circuit of figure 1-4. Figure 1-4.—Practice tank circuit.