Cos=2/3 tính sin tan cot . Tan=3 tính Sin cot cos . Cot=5 tính Sin cos tan

b/ \(\cos^2\alpha=\dfrac{4}{9}\\\cos^2\alpha+\sin^2\alpha=1\\↔\dfrac{4}{9}+\sin^2\alpha=1\\↔\sin^2\alpha=\dfrac{5}{9}\\↔\sin\alpha=\dfrac{\sqrt 5}{3}\\1+\tan^2\alpha=\dfrac{1}{\cos^2\alpha}\\↔1+\tan^2\alpha=\dfrac{9}{4}\\↔\tan^2\alpha=\dfrac{5}{4}\\↔\tan\alpha=\dfrac{\sqrt 5}{2}\\\tan\alpha.cot\alpha=1\\↔\dfrac{\sqrt 5}{2}.\cot\alpha=1\\↔\cot\alpha=\dfrac{2}{\sqrt 5}\)

c/ \(\cot\alpha.\tan\alpha 1=\\↔\cot\alpha.3=1\\↔\cot\alpha=\dfrac{1}{3}\\1+\tan^2\alpha=\dfrac{1}{\cos^2\alpha}\\↔10=\dfrac{1}{\cos^2\alpha}\\↔\cos\alpha=\dfrac{1}{\sqrt 10}\\\tan\alpha=\dfrac{\sin\alpha}{\cos\alpha}\\↔3=\dfrac{\sin\alpha}{\dfrac{1}{\sqrt 10}}\\↔\sin\alpha=\dfrac{3}{\sqrt{10}}\)

d/ \(\cot \alpha.\tan\alpha=1\\↔5.\tan\alpha=1\\↔\tan\alpha=\dfrac{1}{5}\\1+\cot^2\alpha=\dfrac{1}{\sin^2\alpha}\\↔1+25=\dfrac{1}{\sin^2\alpha}\\↔\sin^2\alpha=\dfrac{1}{26}\\↔\sin\alpha=\dfrac{1}{\sqrt{26}}\\\sin^2\alpha+\cos^2\alpha=1\\↔\frac{1}{26}+\cos^2\alpha=1\\↔\cos^2\alpha=\dfrac{25}{26}\\↔\cos\alpha=\dfrac{5}{\sqrt{26}}\)