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数学简单三角函数!f(x)=2sin(wx+q)图象过(0,2)(6,0),求函数f(x)的解析式(2)令M=f(x)+

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数学简单三角函数!
f(x)=2sin(wx+q)图象过(0,2)(6,0),求函数f(x)的解析式
(2)令M=f(x)+(1/2)f(-x),求M的最大值
f(x)=2sin(wx+q)图象过(0,2)(6,0)
2=2sin(0+q)
0=2sin(6w+q)
w=±π/12,q=π/2
f(x) = 2sin(-xπ/12+π/2)或f(x) = 2sin(xπ/12+π/2)
因为sinα=sin(π-α)
∴sin(-xπ/12+π/2)=sin[π-(-xπ/12+π/2)]=sin(xπ/12+π/2)
∴f(x) = 2sin(-xπ/12+π/2) 和 f(x) = 2sin(xπ/12+π/2) 是等效函数,可用f(x) = 2sin(xπ/12+π/2)一个式子表达.
M=f(x)+(1/2)f(-x)=2sin(xπ/12+π/2)+1/2*2sin(-xπ/12+π/2)
=2sin(xπ/12+π/2)+sin(-xπ/12+π/2)
=2sin(xπ/12+π/2)+sin(π+xπ/12-π/2)
=3sin(xπ/12+π/2)
-1 ≤ sin(xπ/12+π/2) ≤ 1
-3 ≤ 3sin(xπ/12+π/2) ≤ 3
所以M最大值3