Small-angle approximation

Small angle approximation is a way of estimating angles in radians, where the angle is small (less than 3 or 4 degrees).

When x is small, and in radians, the following formulae are true:

$\sin x\simeq x$

$\cos x\simeq 1-{\frac {x^{2}}{2}}$

$\tan x\simeq x$