Cho \(\cot a = 3\). Khi đó \(\dfrac{{3\sin a - 2\cos a}}{{12{{\sin }^3}a + 4{{\cos }^3}a}}\) có giá trị bằng

\(\cot \alpha  = 2\).

\(\cot \alpha  = \dfrac{1}{4}\).

\(\cot \alpha  = \dfrac{1}{2}\).

\(\cot \alpha  = \sqrt 2 \).

$\dfrac{1}{{{{\left( {a + b} \right)}^2}}}$.

$\dfrac{1}{{{a^2} + {b^2}}}$.

$\dfrac{1}{{{{\left( {a + b} \right)}^3}}}$.

$\dfrac{1}{{{a^3} + {b^3}}}$

$2$.

$-2$.

$1$.

$-1$.

$-a$.

\(a\).

$-b$.

\(b\).

$\tan a > 0$, $\cot a > 0$.

$\tan a < 0$, $\cot a < 0$.

$\tan a > 0$, $\cot a < 0$.

$\tan a < 0$, $\cot a > 0$.

$\dfrac{{5 - \sqrt 7 }}{4}$ hay $\dfrac{{5 + \sqrt 7 }}{4}$.

$\dfrac{{5 - \sqrt 5 }}{7}$ hay $\dfrac{{5 + \sqrt 5 }}{4}$.                  

$\dfrac{{2 - \sqrt 3 }}{5}$ hay $\dfrac{{2 + \sqrt 3 }}{5}$.          

$\dfrac{{3 - \sqrt 2 }}{5}$ hay $\dfrac{{3 + \sqrt 2 }}{5}$.