函数y=cos2x cosπ/5-2sinx cosx sin6π/5的递增区间如题,求递增区间.除了中间一个减号,其余都是乘号 A[kπ+π/10,kπ+3π/5] B[kπ-3π/20,kπ+7π/20] C[2kπ+π/10,2kπ+3π/5] D[kπ-2π/5,kπ+π/10]

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函数y=cos2x cosπ/5-2sinx cosx sin6π/5的递增区间如题,求递增区间.除了中间一个减号,其余都是乘号 A[kπ+π/10,kπ+3π/5] B[kπ-3π/20,kπ+7π/20] C[2kπ+π/10,2kπ+3π/5] D[kπ-2π/5,kπ+π/10]

函数y=cos2x cosπ/5-2sinx cosx sin6π/5的递增区间如题,求递增区间.除了中间一个减号,其余都是乘号 A[kπ+π/10,kπ+3π/5] B[kπ-3π/20,kπ+7π/20] C[2kπ+π/10,2kπ+3π/5] D[kπ-2π/5,kπ+π/10]
函数y=cos2x cosπ/5-2sinx cosx sin6π/5的递增区间
如题,求递增区间.
除了中间一个减号,其余都是乘号
A[kπ+π/10,kπ+3π/5]
B[kπ-3π/20,kπ+7π/20]
C[2kπ+π/10,2kπ+3π/5]
D[kπ-2π/5,kπ+π/10]

函数y=cos2x cosπ/5-2sinx cosx sin6π/5的递增区间如题,求递增区间.除了中间一个减号,其余都是乘号 A[kπ+π/10,kπ+3π/5] B[kπ-3π/20,kπ+7π/20] C[2kπ+π/10,2kπ+3π/5] D[kπ-2π/5,kπ+π/10]
y=cos2x cosπ/5-2sinx cosx sin6π/5
=cos2x cosπ/5-sin2x sin6π/5…………【注意:sin6π/5=-sinπ/5 诱导公式】
=cos2x cosπ/5+sin2x sinπ/5
=cos(2x-π/5)
递增区间:2kπ+π


y=cos2xcosπ/5-2sinxcosxsin6π/5
y=cos2xcosπ/5-sin2xsin6π/5
y=cos2xcosπ/5+sin2xsinπ/5
y=cos(2x-π/5)
又因为余弦函数的递增区间是[π,2π],所以函数定义域就是
π<=2x-π/5<=2π
6π/5<=2x<=11π/5
6π/10<=x<...

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y=cos2xcosπ/5-2sinxcosxsin6π/5
y=cos2xcosπ/5-sin2xsin6π/5
y=cos2xcosπ/5+sin2xsinπ/5
y=cos(2x-π/5)
又因为余弦函数的递增区间是[π,2π],所以函数定义域就是
π<=2x-π/5<=2π
6π/5<=2x<=11π/5
6π/10<=x<=11π/10
若函数定义域是[0,2π]上就不用看后面的了
又因为这是一个周期函数,周期是π,
所以,函数的递增区间是[kπ+6π/10,kπ+11π/10] (k属于整数,)
楼上的不会做别说人家题错了

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