giải giúp e câu 4,5,6 ạ

$4.$

$y=sin\sqrt{4+x^2}$

$y'=\dfrac{2x}{2\sqrt{4+x^2}}.cos\sqrt{4+x^2}=\dfrac{xcos\sqrt{4+x^2}}{\sqrt{4+x^2}}$

$5.$

$y=cot\sqrt{1+x^2}$

$y'=-\dfrac{2x}{2\sqrt{1+x^2}}.\dfrac{1}{sin^2\sqrt{1+x^2}}=\dfrac{-x}{\sqrt{1+x^2}sin^2\sqrt{1+x^2}}$

$6.$

$y=sin^23x$

$y'=(sin^23x)'=2.sin3x.(sin3x)'=2sin3x.3cos3x=6sin3xcos3x$