设-π/6<=x<=π/4,求函数y=log2^(1+sianx)+log2(1-sinx)的最大值和最小值

来源:百度知道 编辑:UC知道 时间:2024/09/23 09:31:27
设-π/6<=x<=π/4,求函数y=log2^(1+sianx)+log2(1-sinx)的最大值和最小值

设-π/6<=x<=π/4,求函数y=log2^(1+sinx)+log2(1-sinx)的最大值和最小值。
函数会不会是这样的:y=log2(1+sinx)+log2(1-sinx)?

y=log2(1+sinx)+log2(1-sinx)=
=log2[1+sinx)(1-sinx)]=
=log2[1-(sinx)^2],
-π/6<=x<=π/4,
sin(-π/6)=-0.5<=sinx<=sin(π/4)=√2/2,
0≤(sinx)^2≤0.5,
0.5≤1-(sinx)^2≤1,
y=log2^(1+sinx)+log2(1-sinx)=
=log2[1-(sinx)^2] 的最大值是0;
最小值是log2(0.5)= -1.
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函数,要么是这样的:
函数y=log2^(1+sinx)+log2^(1-sinx)=
=log(10)[2^(1+sinx)]+log(10)[2^(1-sinx)]=
=lg[2^(1+sinx)]+lg[2^(1-sinx)]=
=lg[2^(1+sinx)*2^(1-sinx)]=
=lg[2^2]=
lg4. 显然,不应该是这样的结果!
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函数,要么按照你的写法:
函数y=log2^(1+sinx)+log2(1-sinx),
-π/6≤x≤π/4,
sin(-π/6)=-0.5≤sinx≤sin(π/4)=√2/2,
0.5≤1+sinx≤1+√2/2,
1-√2/2≤1-sinx≤0.5;

0.5lg2≤log2^(1+sinx)=(1+sinx)lg2≤(1+√2/2)lg2,
log2(1-√2/2)≤log2(1-sinx)≤log2(0.5)=-1;

y=log2^(1+sinx)+log2(1-sinx)=