Question
Using differentials, find the approximate values of the following:
$\log_\text{e}4.04,$ it being given that $\log_{{10}^{4}}=0.6021$ and $\log_{10}\text{e}=0.4343$

Answer

Consider the function  $\text{y}=\text{f}(\text{x})\log_\text {e}\text{x}.$

Let:

x = 4

$\text{x}+\triangle \text{x}=4.04$

Then,

$\triangle\text{x} =0.04$

For x = 4

$\text{y}=\log_\text {e}4=\frac{\log_{10}4}{\log_{10}\text {e}}=\frac{0.6021}{0.4343}=1.386368$

Let:

$\text{dx}=\triangle \text{x}=0.04$

Now, $\text{y}=\log_\text {e}\text{x}$

$\Rightarrow\frac {\text{dy}}{\text{dx}}=\frac{1}{\text {x}}$

$\Rightarrow\Big(\frac {\text{dy}}{\text{dx}}\Big)_{\text{x}=4} =\frac{1}{4}$

$\therefore\triangle \text{y}=\text{dy}=\frac{\text{dy}} {\text{dx}}\text{dx}=\frac{1} {4}\times0.04=0.01$

$\Rightarrow\triangle \text{y}=0.01$

$\therefore\log_\text {e}4.04=\text{y}+\triangle\text{y} =1.39638$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free