Dayalan Saravanan


Logarithms:

lognx = y
then, the value of x = ny
log(a.b) = log a + log b
log(a/b) = log a - log b
lognx = log10x/log10n
if x = ny then, log x = y log n

Number Logarithm Number Logarithm
1 0 11 1.04
2 0.30 12 1.08
3 0.48 13 1.11
4 0.60 14 1.15
5 0.70 15 1.18
6 0.78 16 1.20
7 0.85 17 1.23
8 0.90 18 1.26
9 0.95 19 1.28
10 1.00 20 1.30

By knowing the logarithms of 1, 2, 3, 7 and 10, the logarithm of any number can be found.

Examples:
log 5 = log(10/2) = log 10 - log 2 = 1 - 0.30 = 0.70
log 20 = log(2.10) = log 2 + log 10 = 0.30 + 1 = 1.30