The resonant frequency in a RLC circuit is given by
[tex] f=\frac{1}{2 \pi \sqrt{LC}} [/tex]
where L is the inductance and C the capacitance of the circuit.
By rearranging the equation, we get:
[tex] C=\frac{1}{(2 \pi f)^2 L} [/tex]
and by substituting the inductance of the circuit, [tex] L=21 mH=0.021 H [/tex] and the resonant frequency, [tex] f=1010 Hz [/tex], we find the value of the capacitance we have to add:
[tex] C=\frac{1}{(2 \pi (1010 Hz))^2 (0.021 H)}=1.18 \cdot 10^{-6} C=1.18 \mu C [/tex]
