Where the two reactances cancel
Inductive reactance climbs with frequency and capacitive reactance falls. Put both in one circuit and there is exactly one frequency where they are equal — and being opposite in sign, they cancel completely. That frequency is resonance.
, read aloud f-nought equals one over two pi root L C. is the resonant frequency in hertz, is the inductance in henries and the capacitance in farads. Note there is no resistance in it at all: R does not move where a circuit resonates. Take the root of the product first, then let 2π turn radians per second into hertz — drop that 2π and you have , a real quantity in rad/s, but 6.28 times the number you were asked for.
Resistance decides how SHARPLY it resonates. — Q equals one over R, root L over C. is the quality factor, a bare number with no unit, is the loss resistance in the loop in ohms, and and are as before. The root is the circuit's surge impedance in ohms, and dividing by R makes the whole thing dimensionless. More loss, lower Q, blunter peak — which is why a Q figure is really a statement about resistance.
And Q sets the width. — B W equals f-nought over Q, where is the bandwidth in hertz between the two half-power points either side of the peak. A Q of 100 on a 1 MHz carrier gives a 10 kHz window; that is how a radio picks one station out of the air. Chain the three together — , then , then — and you have described a tuned circuit completely. It is also a rehearsal for the boss.