1)f(x)=(3/2)cos2x, T=2π/2=π 2)x∈[π/8,5π/8], ∴2x∈[π/4,5π/4] y=cosx在[π/4,5π/4]上单调减 ∴y=(3/2)cos2x在[π/8,5π/8]上单调减 ∴f(x)取最大值时x=π/8, 此时f(x)=(3/2)×√2/2=3√2/4
记得采纳啊
1)f(x)=(3/2)cos2x, T=2π/2=π 2)x∈[π/8,5π/8], ∴2x∈[π/4,5π/4] y=cosx在[π/4,5π/4]上单调减 ∴y=(3/2)cos2x在[π/8,5π/8]上单调减 ∴f(x)取最大值时x=π/8, 此时f(x)=(3/2)×√2/2=3√2/4
记得采纳啊