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以10为底2的对数计算

lgx=y 就是说10的y次方等于x lg的意思就是以10为底的对数 一般都用计算器.除非想lg100=10这种,像lg2这种最好是记忆下大概等于多少,有些题有用.lg41.79-lg8.95=lg(41.79/8.95)=0.6692493358

lg2=0+0.1lg2^10=0+0.1lg1024=0.1lg(1000*24)=0.3+0.1lg24=0.3+0.01lg24^10=0.3+0.01lg1.0^10=0.3+0.01lg1.0=0.30

利用lg(ab)=lga+lgb的公式 lg2*lg2+lg20*lg5=lg2*lg2+(lg2+lg10)*lg5=lg2*lg2+lg2*lg5+1*lg5=lg2(lg2+lg5)+lg5=lg2*lg10+lg5=lg2+lg5=lg2*5=lg10=1

log2(8)=3

lg2=0.30103

lg5*lg5+lg2*lg50 =lg5*lg5 + lg2*lg(2*25) =lg5*lg5 + lg2*lg2 + lg2*lg25 =lg5*lg5 + lg2*lg2 + lg2*lg(5) =lg5*lg5 + lg2*lg2 + 2lg2*lg5 (注意到了吗?这是a+2ab+b的形式.) =(lg5+lg2) =[lg(5*2)] =1 =1

log以10为底45的对数是约1.653.

2一>log

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