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log2Cos20度+log2Cos40度+log2Cos80度

log2cosπ9+log2cos2π9+log2cos4π9=log2(cosπ9?cos2π9?cos49π)=log2(sin2π92sinπ9?sin4π92sin2π9?sin8π92sin4π9)=log218=-3.

log2(cosπ/9)+log2(cos(2π)/9)+log2(cos(4π)/9 =log2(cosπ/9*cos2π/9*cos4π/9) =log2[(2sinπ/9*cosπ/9*cos2π/9*cos4π/9)/2sinπ/9] =log2[(sin2π*cos2π/9*cos4π/9)/2sinπ/9] =log2[(sin4π/9*cos4π/9)/4sinπ/9] =log2[(sin8π/9)/(8sinπ/9)] =-3 麻...

log2(cos20°)+log2(cos40°+log2(cos80°) =log2(cos20°*cos40°*cos80°) =log2(sin20cos20cos40cos80/sin20) =log2(1/2*sin40cos40cos80/sin20) =log2(1/4*sin80cos80/sin20) =log2(1/8*sin160/sin20) =log2(1/8) =-3

利用2倍角公式 cosπ/9*cos2π/9*cos4π/9 =[sinπ/9*cosπ/9*cos2π/9*cos4π/9]/sinπ/9 =[1/2sin2π/9*cos2π/9*cos4π/9]/sinπ/9 =[1/4sin4π/9*cos4π/9]/sinπ/9 =[1/8sin8π/9]/sinπ/9 =[1/8sinπ/9]/[sinπ/9] =1/8 log2cosπ/9+log2cos2π/9+log2cos4π/9 =...

闭区间 KPAI-6分之PAI,KPAI+3分之PAI K属于整数 设Y=sint 因为sint的单调增区间在[2kpia-2/pai,2kpai+2/pai] 所以2kpai-2/pai≤2x-6/pai≤

(1)∵32sinx+cos2x-32>0,∴(2sinx-1)(sinx-1)<0,∴12<sinx<1,∴2kπ+π6<x<2kπ+π2,或2kπ+5π6<x<2kπ+π,即函数f(x)的定义域为:(2kπ+π6,2kπ+π2)∪(2kπ+5π6,2kπ+π);令g(x)=32sinx+cos2x-32=-(sinx?34)2+116,∴g(x)在(12...

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原式=log2(cosπ/9cos2π/9cos4π/9) =log2[(2sinπ/9cosπ/9cos2π/9cos4π/9)/2sinπ/9] =log2[(sin2π/9cos2π/9cos4π/9)/2sinπ/9] =log2[(2sin2π/9cos2π/9cos4π/9)/4sinπ/9] =log2[(sin4π/9cos4π/9)/4sinπ/9] =log2(sin8π/9/8sinπ/9) =log2(sinπ/9/8si...

(1) y=log2(x^2)-log2(x) =2log2(x)-log2(x) =log2(x) y'=1/(xln2) (2) y=-2sin(x/2)(-cos(x/2))............余弦二倍角公式 =2sin(x/2)cos(x/2) =sinx....................正弦二倍角公式 y'=cosx 如果你认可我的回答,请点击“采纳为满意答案”,...

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