Toán Lớp 11: Cho cos x = -3/5 và π/2 < x < π. Tính sin x , tan x, cot x
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Toán Lớp 11: Cho cos x = -3/5 và π/2 < x < π. Tính sin x , tan x, cot x
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\dfrac{\pi }{2} < x < \pi \to \sin x > 0,\cos x < 0\\
\cos x = – \sqrt {1 – {{\sin }^2}x} = – \sqrt {1 – {{\left( { – \dfrac{3}{5}} \right)}^2}} = – \dfrac{4}{5}\\
\tan x = \dfrac{{\sin x}}{{\cos x}} = – \dfrac{3}{5}:\dfrac{{ – 4}}{5} = \dfrac{3}{4}\\
\cot x = \dfrac{1}{{\tan x}} = \dfrac{4}{3}
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