Question

What is the value of log13

Answer 1

log 10=1,

log 2= 0.3010, and  

log 3= 0.4771.

From these values, we can find many other log values.  

log 5 = log 10 - log 2 = 0.699

log 0.5 = 0–log 2 = -0.301

log 1.5 = log 3 - log 2 = 0.1761

log 2.5 = log 5 - log 2 = 0.398

To find log of any number y:

Express y as (10^m)*(2^n)*(3^p)*(1+x).

Approximate log(1+x) as

(0.4343)*(x-x^2/2+x^3/3)

Or 0.4353*(x-x^2/2)

log y =

m + 0.3010*n + 0.4771*p + (0.4353)*(x-x^2/2+x^3/3)

To find log 13

13=2^2*3*(1+1/12)

log 13

= 2*0.3010 + 0.4771 + (0.4353)*(1/12 - 1/288+1/5184)

= 0.6020 + 0.4771 + 0.034847

= 1.1139