Question

Найдите sinα, tgα, сtgα если cosα=8/17
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Answer 1

$sin \alpha =\pm\sqrt{1-\cos^2\alpha } =\pm\sqrt{1-\frac{64}{289} } =\pm \sqrt{\frac{225}{289} } =\pm \frac{15}{17} \\tg \alpha = \frac{\sin \alpha }{\cos \alpha } =\pm \frac{15}{17} : \frac{8}{17} =\pm \frac{15}{17} \cdot \frac{17}{8} = \pm \frac{15}{8} \\ctg \alpha =\frac{1}{tg\alpha } =\pm \frac{8}{15}$