Đáp án:

`y = tan(12x)`

`y’’ = [tan(12x)]’’`

`= (((12x)’)/(Cos^2 12x))’`

`= (12/(Cos^2 12x))’`

`= (-(cos^2 12x)’ .12)/(Cos^4 12x)`

`= (-12.2.cos12x.(cos12x)’)/(cos^4 12x)`

`= (-24cos12x.12.(-sin12x))/(cos^4 12x) `

`= (288sin12x.cos12x)/(cos^4 12x)`

`= (144sin24x)/(cos^4 12x)`