Question

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Известно что sina=3/5 и пи

Answer 1

$\sin\alpha=-\frac35,\;\;\pi<\alpha<\frac{3\pi}2\\\sin^2\alpha+\cos^2\alpha=1\Rightarrow\cos\alpha=\sqrt{1-\sin^2\alpha}\\\cos\alpha=\sqrt{1-\left(-\frac35\right)^2}=\sqrt{1-\frac9{25}}=\sqrt{\frac{16}{25}}=\pm\frac45\\\pi<\alpha<\frac{3\pi}2\Rightarrow\cos\alpha<0\\\\\cos\alpha=-\frac45\\tg\alpha=\frac{\sin\alpha}{\cos\alpha}=\left(-\frac35\right):\left(-\frac45\right)=\frac35\cdot\frac54=\frac34\\\\ctg\alpha=\frac1{tg\alpha}=\frac43=1\frac13$