作业帮 > 数学 > 作业

知函数f(x)=2asinxcosx+2bcos^2x,且f(0)=8,f(π/6)=6+3√3/2,求f(x)的最小正

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/29 05:10:32
知函数f(x)=2asinxcosx+2bcos^2x,且f(0)=8,f(π/6)=6+3√3/2,求f(x)的最小正周期与最值
f(x) = 2asinxcosx+2bcos^2x = asin2x+b(cos2x+1) = asin2x+bcos2x+b
f(0) = 8,asin0+bcos0+b = 0+b+b=8,b=4
f(x) = asin2x+4cos2x+4
f(π/6)=6+3√3/2,asinπ/3+4cosπ/3+4 = a√3/2+2+4 = 6+3√3/2,a=3
f(x) = 3sin2x+4cos2x+4
令sint=4/5,cost=3/5
f(x) = 5(sin2xcost+cos2xsint)+4 = 5sin(2x+t) + 4
最小正周期 = 2π/2 = π
-1≤sin(2x+t)≤1
最小值-5+4=-1
最大值5+4=9