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高中数学必修 第一册(648题)


第541题

不等式1+tanx≥0的解集是___.



参考答案:\(\left \{ {x|k\pi -\frac {\pi } {4}\leq x<k\pi +\frac {\pi } {2},k\in Z} \right \} \)




第544题


A.\(f\left ( {x} \right )=\left | {\cos {2x}} \right |\)

B.\(f\left ( {x} \right )=\sin {\left | {2x} \right |}\)

C.\(f\left ( {x} \right )=\left | {\cos {x}} \right |\)

D.\(f\left ( {x} \right )=\left | {\sin {x}} \right |\)


参考答案:C



第546题



参考答案:\([2k\pi ,2k\pi +\frac {\pi } {2}](k\in Z)\)


第547题



参考答案:\(f(x) = \sin (\frac{{5\pi }}{6} - 2x) - 2\sin (x - \frac{\pi }{4})\cos (x + \frac{{3\pi }}{4}) = \frac{1}{2}\cos 2x + \frac{{\sqrt 3 }}{2}\sin 2x + (\sin x - \cos x)(\sin x + \cos x) = \sin (2x - \frac{\pi }{6})\)由 \(2k\pi -\frac {\pi } {2}⩽2x-\frac {\pi } {6}⩽2k\pi +\frac {\pi } {2},k\in Z\),解得\(k\pi -\frac {\pi } {6}⩽x⩽k\pi +\frac {\pi } {3},k\in Z\) ,

所以\(f(x)\)的单调增区间为\([k\pi -\frac {\pi } {6},k\pi +\frac {\pi } {3}],k\in Z\) ;


解析:




第548题



参考答案:


因为\(x \in [0,\frac{{7\pi }}{{12}})\),所以设\(t = 2x - \frac{\pi }{6}\) ,则\(t \in [ - \frac{\pi }{6},\pi )\) ,



所以 \(f(x) = \sin (2x - \frac{\pi }{6}) \in [ - \frac{1}{2},1]\)\(y = |\sin t|\) 的图象如图,



要使\(y = |\sin t| - m\)\([ - \frac{\pi }{6},\pi )\)有两个零点,则\(\frac{1}{2} < m < 1\),故\(m\)的取值范围是\(\left ( {\frac {1} {2},1} \right )\)





解析:





第550题



参考答案:\(\because \) 函数 \(f(x) = {\cos ^2}x + \sqrt 3 \sin x\cos x - \frac{1}{2} = \frac{1}{2}\cos 2x + \frac{{\sqrt 3 }}{2}\sin 2x = \sin (2x + \frac{\pi }{6})\) ,故 \(f(x)\) 的最小正周期为 \(\frac{{2\pi }}{2} = \pi \) .


解析:




第551题



参考答案:令\(2k\pi -\frac {\pi } {2}\leq 2x+\frac {\pi } {6}\leq 2k\pi +\frac {\pi } {2}\),求得\(k\pi -\frac {\pi } {3}\leq x\leq k\pi +\frac {\pi } {6},\left ( {k\in Z} \right )\),

可得函数的增区间为\(\left [ {k\pi -\frac {\pi } {3},k\pi +\frac {\pi } {6}} \right ],\left ( {k\in Z} \right )\).


解析:




第552题


A.\(\left [ {-\frac {\pi } {6},\frac {\pi } {3}} \right ]\)

B.\(\left [ {\frac {5\pi } {12},\frac {11\pi } {12}} \right ]\)

C.\(\left [ {-\frac {5\pi } {12},\frac {\pi } {12}} \right ]\)

D.\(\left [ {-\frac {11\pi } {12},-\frac {5\pi } {12}} \right ]\)


参考答案:B





第556题


A.\((0,\frac {1} {6}]\cup \left [ {\frac {1} {3},\frac {3} {4}} \right ]\)

B.\((0,\frac {1} {3}]\cup \left [ {\frac {2} {3},\frac {3} {4}} \right ]\)

C.\((0,\frac {1} {6}]\cup \left [ {\frac {1} {3},\frac {2} {3}} \right ]\)

D.\((0,\frac {1} {3}]\cup \left [ {\frac {2} {3},\frac {5} {6}} \right ]\)


参考答案:C


第557题



参考答案:\(f(x) = \sin (2x - \frac{\pi }{6}) + 2{\cos ^2}x - 1 = \frac{{\sqrt 3 }}{2}\sin 2x - \frac{1}{2}\cos 2x + \cos 2x = \frac{{\sqrt 3 }}{2}\sin 2x + \frac{1}{2}\cos 2x = \sin (2x + \frac{\pi }{6})\)

由 \(2k\pi - \frac{\pi }{2}⩽2x + \frac{\pi }{6}⩽2k\pi + \frac{\pi }{2}(k \in Z)\) ,得\(k\pi -\frac {\pi } {3}⩽x⩽k\pi +\frac {\pi } {6}(k\in Z)\),

所以 \(f(x)\) 的单调增区间是\(\left [ {k\pi -\frac {\pi } {3},k\pi +\frac {\pi } {6}} \right ](k\in Z)\);


解析:




第558题



参考答案:\(\because x\in \left [ {0,m} \right ]\),\(2x+\frac {\pi } {6}\in \left [ {\frac {\pi } {6},2m+\frac {\pi } {6}} \right ]\) ,\(f\left ( {x} \right )\in \left [ {\frac {1} {2},1} \right ]\),

\(\therefore \) \(\frac{\pi }{2}⩽2m + \frac{\pi }{6}⩽\frac{{5\pi }}{6}\) ,\(\therefore \) \(\frac{\pi }{6}⩽m⩽\frac{\pi }{3}\) ,

故实数 \(m\) 的取值范围为\(\left [ {\frac {\pi } {6},\frac {\pi } {3}} \right ]\).


解析:




第559题


A.\(\left ( {2kπ-π,2kπ} \right )\),\(k\in Z\)

B.\(\left ( {2kπ,2kπ+π} \right )\),\(k\in Z\)

C.\(\left ( {2kπ-\frac {7π} {6},2kπ-\frac {π} {6}} \right )\),\(k\in Z\)

D.\(\left ( {2kπ-\frac {π} {6},2kπ+\frac {5π} {6}} \right )\),\(k\in Z\)


参考答案:C



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