\(\eqalign{ & df\left( {{x_0}} \right) = f'\left( {{x_0}} \right)\Delta x.\,\text{ Ta có }\,f'\left( x \right) = 2\cos 2x \cr & df\left( {{\pi \over 3}} \right) = 2\cos {{2\pi } \over 3}.\Delta x = - \Delta x \cr} \)
Với \(\Delta x = 0,01\,\text{ thì }\,df\left( {{\pi \over 3}} \right) = - 0,01\)
Với \(\Delta x = 0,001\,\text{ thì }\,df\left( {{\pi \over 3}} \right) = - 0,001\)
