Đáp án:
$cos\alpha=\dfrac{\sqrt{5}}{3}$
$tan\alpha=\dfrac{2}{\sqrt{5}}$
$cot\alpha=\dfrac{\sqrt{5}}{2}$
Giải thích các bước giải:
Ta có: $sin^2\alpha+cos^2\alpha=1$
$⇔cos^2\alpha=1-\bigg(\dfrac{2}{3}\bigg)^2$
$⇔cos^2\alpha=\dfrac{5}{9}$
$⇒cos\alpha=\sqrt{\dfrac{5}{9}}=\dfrac{\sqrt{5}}{3}$
Ta lại có: $tan\alpha=\dfrac{sin\alpha}{cos\alpha}=\dfrac{\dfrac{2}{3}}{\dfrac{\sqrt{5}}{3}}=\dfrac{2}{\sqrt{5}}$
$⇒cot\alpha=\dfrac{1}{tan\alpha}=\dfrac{1}{\dfrac{2}{\sqrt{5}}}=\dfrac{\sqrt{5}}{2}$
