Tính sin, cos, tan, cot góc 30, 45, 60 độ

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$\begin{array}{|c|c|c|}\hline \alpha&30^o&45^o&60^o\\\hline \sin \alpha&\dfrac12&\dfrac{\sqrt2}{2}&\dfrac{\sqrt3}2\\\hline \cos \alpha&\dfrac{\sqrt3}2&\dfrac{\sqrt2}2&\dfrac12\\\hline \tan \alpha&\dfrac{\sqrt3}3&1&\sqrt3\\\hline \cot \alpha&\sqrt3&1&\dfrac{\sqrt3}3\\\hline\end{array}$