已知函数f(x)=sin(2x+π6)−cos(2x+π3)+2cos2x.

问题描述:

1个回答 分类:数学 2014-12-06

问题解答:

我来补答
(1)f(
π
12)=sin(2×
π
12+
π
6)-cos(2×
π
12+
π
3)+2cos2
π
12=sin
π
3-cos
π
2+1+cos
π
6=

3
2-0+1+

3
2
=
3+1
(2)∵f(x)=sin(2x+
π
6)-cos(2x+
π
3)+2cos2x
=sin2xcos
π
6+cos2xsin
π
6-cos2xcos
π
3+sin2xsin
π
3+cos2x+1
=
3sin2x+cos2x+1=2sin(2x+
π
6)+1,
∴当sin(2x+
π
6)=1时,f(x)max=2+1=3,
此时,2x+
π
6=2kπ+
π
2,即x=kπ+
π
6(k∈Z),
 
 
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