blackgeo
幼苗
共回答了24个问题采纳率:79.2% 举报
向量a=(2cosx,cos2x),b=(sinx,√3),
函数f(x)=a*b=2sinxcosx+√3cos2x
=sin2x+√3cos2x
=2(1/2*sin2x+√3/2*cos2x)
=2sin(2x+π/3)
1º函数y=2sinx的图像向左平移π/3得到y=sin(x+π/3)的图象;
2º y=sin(x+π/3)的图象上每一点纵坐标不变,横坐标变为原来的1/2倍得到y=sin(2x+π/3)的图像
3ºy=sin(2x+π/3)的图像上每一点横坐标不变,纵坐标变为原来的2倍得到y=f(x)的图像
(2) ∵x∈ [0,π/2] ∴2x+π/3∈[π/3,4π/3]
∴2x+π/3=π/2时,f(x)取得最大值2
2x+π/3=4π/3时,f(x)取得最小值-√3
(3)∵f(x0)=6/5 ∴2sin(2x0+π/3)=6/5
∴sin(2x0+π/3)=3/5
1年前
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