共50条信息
\(MP\),\(OM\),\(AT\)分别为\(θ(\)\( < θ < \)\()\)的正弦线、余弦线、正切线,则一定有( )
若\(- \dfrac{3π}{4} < α < - \dfrac{π}{2}\),从单位圆中的三角函数线观察\(\sin α\),\(\cos α\),\(\tan α\)的大小是\((\) \()\)
设\(a=\sin 2\),\(b=\cos 2\),\(c=\tan 2\),则\(a\),\(b\),\(c\)的大小关系是( )
若\(α∈\left( \left. 0, \dfrac{π}{2} \right. \right)\),则\(\tan α > \sin α.(\) \()\)
\(\sin x{ < }\dfrac{\sqrt{2}}{2}\)的\(x\)取值范围为______ .
已知点\(P(\tan \alpha ,\cos \alpha )\)在第三象限,则角\(\alpha \)在 \((\) \()\)
已知函数\(f(x)=\sqrt{3}\cos (2x-\dfrac{\pi }{3})-2\sin x\cos x\).
\((I)\)求\(f\)\((\)\(x\)\()\)的最小正周期;
\((II)\)求证:当\(x\in [-\dfrac{\pi }{4},\dfrac{\pi }{4}]\)时,\(f\left( x \right)\geqslant -\dfrac{1}{2}\).
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