已知log以3为底的2=a,log5以5为底的3=b,则log以2为底的5=

问题描述:

已知log以3为底的2=a,log5以5为底的3=b,则log以2为底的5=

因:log3(2)=a 可得:lg2/lg3=a 即:lg2=alg3
log5(3)=b 可得:lg3/lg5=b 得:lg5=lg3/b
log2(5)=lg5/lg2=(lg3/b)/(alg3)=1/(ab)

log2 5=log2 3×log3 5=ab

解析
log3 2=a
log5 3=b
log2 5
=lg2/lg5
=log3 2/log3 5
=ab