This applet is a calculator for the equation:

This applet can be used to calculate the phase angle (q) when the inductance (X) and the resistance (R) of
a circuit are known. Alternately, when the phase angle and either the reactance or the resistance is known,
the other variable can be calculated. Note that the capacitive reactance term has been included in the
applet, but in eddy current testing this value is small and a zero value can be used.