Find the derivative of $21$ using the constant rule

Find the derivative

$\frac{d}{dx}\left(\pi100^2=0\right)$

$\frac{d}{dx}\left(\arctan\left(x-\sqrt{1+x^2}\right)\right)$

$\frac{d}{dx}\arctan\left(x-\sqrt{1+x^2}\right)$

$\frac{d}{dx}\arccos\left(\sqrt{1-x^2}\right)$

$\frac{d}{dx}\left(\mathrm{sech}\left(-4x\right)\left(1-\ln\left(\mathrm{sech}\left(-4x\right)\right)\right)\right)$

$\frac{d}{dx}\left(2x^3\tanh\left(\frac{1}{x^2}\right)\right)$

$\frac{d}{dx}\left(\ln\left(\mathrm{sech}\left(3x+8\right)\right)\right)$