求log以2为底cosπ/9的对数+log以2为底cos2π/9+log以2为底4π/9=

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同底的对数相加,结果等于真数积的对数
真数之积为
cosπ/9cos2π/9cos4π/9
=(8sinπ/9cosπ/9cos2π/9cos4π/9)/(8sinπ/9)
=4sin2π/9cos2π/9cos4π/9)/(8sinπ/9)
=(2sin4π/9cos4π/9)/(8sinπ/9)
=(sin8π/9)/(8sinπ/9)
=(sin(π-π/9))/(8sinπ/9)
=1/8
所以log2 (1/8)=-3,即原式=-3

求log以2为底cosπ/9的对数+log以2为底cos2π/9+log以2为底4π/9= log以2为底25的对数乘log以3为底4的对数乘log以5为底9的对数=? 计算：（log以4为底3的对数+log以8为底3的对数）（log以3为底2的对数+log以9为底2的对数）- log以½ log以4为底8的对数-log以9分之1为底3的对数-log以根号2为底4的对数 log以2为底25的对数乘以log以3为底4的对数乘以log以5为底9的对数 log以2为底25的对数+log以3为底4的对数+log以5为底9的对数 log以3为底2的对数+log以9为底2的对数的和,乘以,log以4为底3的对数+log 以8为底3的对数的和,的积 2log以3为底2的对数-log以3为底32/9的对数+log以3为底8的对数-5的2倍log以5为底3的对数 =多少? 化简（log以4为底3的对数+log以8为底3的对数）乘（log以3为底2的对数+log以9为底2的对数）（log以4为底3的对数+log以8为底3的对数）*（log以3为底2的对数+log以9为底2的对数） log以3为底的2的对数为什么等于log以9为底的4的对数 log以2为底9的对数乘于log以3为底4的对数怎么算!