f(x)=3sin(ωx+π/6),ω>0,x∈R,且以π/2为最小正周期.f(α/4+π/12)=9/5,求sin(π
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f(x)=3sin(ωx+π/6),ω>0,x∈R,且以π/2为最小正周期.f(α/4+π/12)=9/5,求sin(π/4+2α)
![f(x)=3sin(ωx+π/6),ω>0,x∈R,且以π/2为最小正周期.f(α/4+π/12)=9/5,求sin(π](/uploads/image/z/17862528-48-8.jpg?t=f%28x%29%3D3sin%28%CF%89x%2B%CF%80%2F6%29%2C%CF%89%3E0%2Cx%E2%88%88R%2C%E4%B8%94%E4%BB%A5%CF%80%2F2%E4%B8%BA%E6%9C%80%E5%B0%8F%E6%AD%A3%E5%91%A8%E6%9C%9F.f%28%CE%B1%2F4%2B%CF%80%2F12%29%3D9%2F5%2C%E6%B1%82sin%28%CF%80)
∵f(x)以π/2为最小正周期
∴2π/ω=π/2
∴ω=4
∴f(x)=3sin(4x+π/6)
∵f(α/4+π/12)=9/5
∴3sin(α+π/3+π/6)=3sin(α+π/2)=9/5
∴cosα=3/5
∴sinα=±√(1-3²/5²)=±4/5
∴sin2α=2sinαcosα=±24/25
cos2α=2cos²α-1=-7/25
∴sin(π/4+2α)=(√2/2)(sin2α+cos2α)
=(√2/2)(±24/25-7/25)
=(√2/2)(17/25)或(√2/2)(-31/25)
=(17√2)/50或(-31√2)/50
∴2π/ω=π/2
∴ω=4
∴f(x)=3sin(4x+π/6)
∵f(α/4+π/12)=9/5
∴3sin(α+π/3+π/6)=3sin(α+π/2)=9/5
∴cosα=3/5
∴sinα=±√(1-3²/5²)=±4/5
∴sin2α=2sinαcosα=±24/25
cos2α=2cos²α-1=-7/25
∴sin(π/4+2α)=(√2/2)(sin2α+cos2α)
=(√2/2)(±24/25-7/25)
=(√2/2)(17/25)或(√2/2)(-31/25)
=(17√2)/50或(-31√2)/50
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