Question

biết cos a=\(\dfrac{20}{29}\). tính sin a, tan a, cot a

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Answer 1

*Ta có \(\cos^2a+\sin^2a=1\)

\(\Rightarrow sina=\sqrt{1-\cos^2a}=\sqrt{1-\left(\dfrac{20}{29}\right)^2}=\dfrac{21}{29}\)

*Ta có \(\tan a=\dfrac{\sin a}{\cos a}=\dfrac{21}{29}:\dfrac{20}{29}=\dfrac{21}{20}\)

*Ta có \(\cot a.\tan a=1\Rightarrow\cot a=\dfrac{1}{\tan a}=\dfrac{20}{21}\)

Answer 2

\(\sin\alpha=\sqrt{1-\left(\dfrac{20}{29}\right)^2}=\dfrac{21}{29}\)

\(\tan\alpha=\dfrac{21}{20}\)

\(\cot\alpha=\dfrac{20}{21}\)