Answer
Verified
420k+ views
Hint: For solving this problem, the expansion of ${{e}^{x}}$ is required in terms of x. By using this expansion and putting x as $-\dfrac{1}{5}$, we can evaluate the required value correctly up to 4 decimal places.
Complete step-by-step answer:
In our question, we are required to evaluate the value of ${{e}^{-\dfrac{1}{5}}}$ correct to four decimal places. First, we write the expansion of ${{e}^{x}}$ in terms of x up to infinity and then put the value of x in that expression to calculate the value ${{e}^{-\dfrac{1}{5}}}$ correct up to 4 decimal places. So, the expansion of is ${{e}^{x}}$:
${{e}^{x}}=1+x+\dfrac{{{x}^{2}}}{2!}+\dfrac{{{x}^{3}}}{3!}+\dfrac{{{x}^{4}}}{4!}+......\text{ }to\text{ }\infty \text{ }\ldots (1)$
Now, putting the value of x in equation (1) as $x=-\dfrac{1}{5}$, we get
${{e}^{-\dfrac{1}{5}}}=1-\dfrac{1}{5}+\dfrac{1}{2!}\cdot {{\left( -\dfrac{1}{5} \right)}^{2}}+\dfrac{1}{3!}\cdot {{\left( -\dfrac{1}{5} \right)}^{3}}+\dfrac{1}{4!}\cdot {{\left( -\dfrac{1}{5} \right)}^{4}}.......\infty $
Now, simplifying each term by multiplication, we get
$\begin{align}
& {{e}^{-\dfrac{1}{5}}}=1-\dfrac{1}{5}+\dfrac{1}{50}-\dfrac{1}{750}+\dfrac{1}{15000}.......\infty \\
& {{e}^{-\dfrac{1}{5}}}=1-0.2+0.02-0.001333+0.0000066 \\
& {{e}^{-\dfrac{1}{5}}}=0.8187 \\
\end{align}$
So, the correct value of ${{e}^{-\dfrac{1}{5}}}$ to four decimal places is 0.8187.
Note: The key step in solving this problem is the knowledge of series expansion of various functions of x. Students must be careful while putting the value of x in the expansion. They must take care of the negative sign and power associated with sign to avoid errors in calculation.
Complete step-by-step answer:
In our question, we are required to evaluate the value of ${{e}^{-\dfrac{1}{5}}}$ correct to four decimal places. First, we write the expansion of ${{e}^{x}}$ in terms of x up to infinity and then put the value of x in that expression to calculate the value ${{e}^{-\dfrac{1}{5}}}$ correct up to 4 decimal places. So, the expansion of is ${{e}^{x}}$:
${{e}^{x}}=1+x+\dfrac{{{x}^{2}}}{2!}+\dfrac{{{x}^{3}}}{3!}+\dfrac{{{x}^{4}}}{4!}+......\text{ }to\text{ }\infty \text{ }\ldots (1)$
Now, putting the value of x in equation (1) as $x=-\dfrac{1}{5}$, we get
${{e}^{-\dfrac{1}{5}}}=1-\dfrac{1}{5}+\dfrac{1}{2!}\cdot {{\left( -\dfrac{1}{5} \right)}^{2}}+\dfrac{1}{3!}\cdot {{\left( -\dfrac{1}{5} \right)}^{3}}+\dfrac{1}{4!}\cdot {{\left( -\dfrac{1}{5} \right)}^{4}}.......\infty $
Now, simplifying each term by multiplication, we get
$\begin{align}
& {{e}^{-\dfrac{1}{5}}}=1-\dfrac{1}{5}+\dfrac{1}{50}-\dfrac{1}{750}+\dfrac{1}{15000}.......\infty \\
& {{e}^{-\dfrac{1}{5}}}=1-0.2+0.02-0.001333+0.0000066 \\
& {{e}^{-\dfrac{1}{5}}}=0.8187 \\
\end{align}$
So, the correct value of ${{e}^{-\dfrac{1}{5}}}$ to four decimal places is 0.8187.
Note: The key step in solving this problem is the knowledge of series expansion of various functions of x. Students must be careful while putting the value of x in the expansion. They must take care of the negative sign and power associated with sign to avoid errors in calculation.
Recently Updated Pages
The branch of science which deals with nature and natural class 10 physics CBSE
The Equation xxx + 2 is Satisfied when x is Equal to Class 10 Maths
Define absolute refractive index of a medium
Find out what do the algal bloom and redtides sign class 10 biology CBSE
Prove that the function fleft x right xn is continuous class 12 maths CBSE
Find the values of other five trigonometric functions class 10 maths CBSE
Trending doubts
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
Write an application to the principal requesting five class 10 english CBSE
Difference Between Plant Cell and Animal Cell
a Tabulate the differences in the characteristics of class 12 chemistry CBSE
Change the following sentences into negative and interrogative class 10 english CBSE
What organs are located on the left side of your body class 11 biology CBSE
Discuss what these phrases mean to you A a yellow wood class 9 english CBSE
List some examples of Rabi and Kharif crops class 8 biology CBSE