Ta có :
* sin2α + cos2α = 1
\(\Leftrightarrow\dfrac{3}{4}\) + cos2α = 1
\(\Leftrightarrow\) cos2α \(=\dfrac{1}{4}\)
\(\Leftrightarrow\) cosα = \(\dfrac{1}{2}\)
* tanα = \(\dfrac{sin\alpha}{cos\alpha}=\dfrac{\sqrt{3}}{2}:\dfrac{1}{2}=\sqrt{3}\)
* tanα . cotα = 1
\(\Leftrightarrow\sqrt{3}.cot\alpha=1\)
\(\Leftrightarrow cot\alpha=\dfrac{1}{\sqrt{3}}=\dfrac{\sqrt{3}}{3}\)