解:
y=sin2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629309225.gif)
cos2
x-2=2sin(2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629418228.gif)
)-2.
(1)列表
x
| -![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629434235.gif)
| ![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629356255.gif)
| ![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
| π
| π
|
2x+![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
| 0
| ![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629528226.gif)
| π
| π
| 2π
|
y=2sin(2x+ )-2
| -2
| 0
| -2
| -4
| -2
|
其图象如下图所示.
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/201408231246295901086.gif)
(2)
T=
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629340257.gif)
=π.
由-
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629528226.gif)
+2
kπ≤2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
≤
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629528226.gif)
+2
kπ,知函数的单调增区间为[-
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629356256.gif)
π+
kπ
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629356255.gif)
+
kπ],
k∈Z;
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629528226.gif)
+2
kπ≤2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
≤
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629559223.gif)
π+2
kπ,知函数的单调减区间为[
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629356255.gif)
+
kπ,
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629387250.gif)
π+
kπ],
k∈Z.
(3)由2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
=
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629528226.gif)
+
kπ得
x=
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629356255.gif)
+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629855234.gif)
π.
∴函数图象的对称轴方程为
x=
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629356255.gif)
+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629855234.gif)
π(
k∈Z).
(4)把函数
y1=sin
x的图象上所有的点向左平移
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
个单位,得到函数
y2=sin(
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
)的图象;
再把
y2图象上各点的横坐标缩短到原来的
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629949225.gif)
倍(纵坐标不变),得到
y3=sin(2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
)的图象;
再把
y3图象上各点的纵坐标伸长到原来的2倍(横坐标不变),得到
y4=2sin(2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
)的图象;
最后把
y4图象上所有的点向下平移2个单位,得到函数
y=2sin(2
x+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124629465227.gif)
)-2的图象.
评注:(1)求函数的周期、单调区间、最值等问题,一般都要化成一个角的三角函数形式.
(2)对于函数
y=
Asin(
ωx+
![](http://thumb.1010pic.com/pic2/upload/papers/20140823/20140823124630027199.gif)
)的对称轴,实际上就是使函数
y取得最大值或最小值时的
x值.
(3)第(4)问的变换方法不唯一,但必须特别注意平移变换与伸缩变换的先后顺序.