How do you use the Change of Base Formula and a calculator to evaluate the logarithm #log_9 2.15#?

1 Answer
Gió
Sep 16, 2015

I found: #0.3483#

Explanation:

The Change of Base Formula allows you to write:

#log_ab=(log_cb)/(log_ca)#
and change your base from #a# to the new base #c#.

We can choose, as new base, #e# and use natural logs, #ln#, that can be evaluated using a pocket calculator and get:

#log_9(2.15)=(ln2.15)/(ln9)=0.3483#

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