Ta có $\pi\approx\sqrt{10}$
$\omega=\dfrac{1}{\sqrt{LC}}=2\pi f$
$\to f=\dfrac{1}{2\pi\sqrt{2.10^{-3}.2.10^{-12}}}$
$=\dfrac{1}{2.\sqrt{10}.\sqrt{4.10^{-15}} }$
$=\dfrac{1}{2.\sqrt{4.10.10^{-15}}}$
$=\dfrac{1}{2.\sqrt{4.(10^{-7})^2}}$
$=\dfrac{1}{2.2.10^{-7}}$
$=\dfrac{1}{4}.10^7=\text{2 500 000}(Hz)$