Đáp án+Giải thích các bước giải:
$cos\alpha=\dfrac{15}{17}$
$sin^2\alpha+cos^2\alpha=1$
$⇒sin^2\alpha=1-cos^2\alpha=1-(\dfrac{15}{17})^2=\dfrac{64}{289}$
$⇒sin\alpha=\dfrac{8}{17}$
$1+cot^2\alpha=\dfrac{1}{sin^2\alpha}$
$⇒cot^2\alpha=\dfrac{1}{sin^2\alpha}-1=\dfrac{1}{\dfrac{64}{289}}-1=\dfrac{225}{64}$
$⇒cot\alpha=\dfrac{15}{8}$
$⇒tan\alpha=\dfrac{1}{cot\alpha}=\dfrac{8}{15}$
