How do you evalute Log_ 3 (18)log3(18)?

1 Answer
Jan 1, 2016

log_3(18)=2+log_3(2)approx2.6309log3(18)=2+log3(2)2.6309

Explanation:

log_3(18)=log_3(3^2xx2)log3(18)=log3(32×2)

Use the rule: log_a(bc)=log_a(b)+log_a(c)loga(bc)=loga(b)+loga(c)

=>log_3(3^2)+log_3(2)log3(32)+log3(2)

Use the rule: log_a(a^b)=bloga(ab)=b

=>2+log_3(2)2+log3(2)

This is a simplified answer. However, if you want your answer in decimal form, use a calculator. Since many calculators don't have the capability of finding logarithms with a specific base, use the change of base formula.

log_a(b)=(log_c(b))/(log_c(a))loga(b)=logc(b)logc(a)

Thus, since the lnln button is on most calculators (or just the loglog button),

log_3(2)=ln(2)/ln(3)=log(2)/log(3)approx0.6309log3(2)=ln(2)ln(3)=log(2)log(3)0.6309

Thus,

log_3(18)=2+log_3(2)approx2.6309log3(18)=2+log3(2)2.6309