函数f(x)=2asin²x-2根号3asinxcosx+a+b,x∈[0,π/2],值域为[-5,1],求a、b
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函数f(x)=2asin²x-2根号3asinxcosx+a+b,x∈[0,π/2],值域为[-5,1],求a、b
函数f(x)=2asin²x-2根号3asinxcosx+a+b,x∈[0,π/2],值域为[-5,1],求a、b
函数f(x)=2asin²x-2根号3asinxcosx+a+b,x∈[0,π/2],值域为[-5,1],求a、b
2sin^2x=1-cos2x
2sinxcosx=sin2x
f(x)=a-acos2x-a√3sin2x+a+b
=2a+b-2a(cos2xcosπ/3+sin2xsinπ/3)
=2a+b-2acos(2x-π/3)
-5
f(x)=a(1-cos2x)-sqrt(3)asin2x+a+b
=-2a[(1/2)(cos2x)+(sqrt(3)/2)sin2x]+2a+b
=-2asin(2x+π/6)+2a+b
x∈[0,π/2] => sin(2x+π/6)∈[-1/2,1];
显然a不等于0;
当a>0时:f(x)∈[-2a+2a+b,a+2a+b]=[b,...
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f(x)=a(1-cos2x)-sqrt(3)asin2x+a+b
=-2a[(1/2)(cos2x)+(sqrt(3)/2)sin2x]+2a+b
=-2asin(2x+π/6)+2a+b
x∈[0,π/2] => sin(2x+π/6)∈[-1/2,1];
显然a不等于0;
当a>0时:f(x)∈[-2a+2a+b,a+2a+b]=[b,3a+b]=[-5,1]
=> a=2,b=1;
当a<0时:f(x)∈[a+2a+b,-2a+2a+b]=[3a+b,b]=[-5,1]
=> a=-2,b=1;
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