# Thread: Evaluate a logarithmic function

1. ## Evaluate a logarithmic function

Evaluate

I got that the answer is 4 because 7log7 = 1

2. ## Re: Evaluate a logarithmic function

I would suggest that you start with the definition of the logarthm: If $a^b = c$ then $\log_a c = b$. Here 'a' is 7 and 'b' is $\log_7 4$, therefore from the right hand side of the definition $\log_7 c = b = log_7 4$. Hence c = 4, and $7^{\log_7 4} = 4$.

3. ## Re: Evaluate a logarithmic function

You are absolutely right. You can also proceed like this. Let c = 7^(ln4 to the base 7) taking log on both sides we get (lnc to the base 7) = (ln4 to the base 7) and that gices c = 4. Hence 7^(ln4 to the base 7)= 4