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Question

The value (round off to one decimal place) of  \(\mathop \smallint \nolimits_{ - 1}^1 x\;{e^{\left| x \right|}}dx\) ______

Explanation

Given,

Function f(x) = x e|x|

 Integral is -1 to 1.

If f(-x) = f(x) then the function is said to be even function

 If f(-x) = - f(x) then the function is said to be odd function.

 f(-x) = -x e|-x| = -x e|x| = - f(x)

 ∴ The given function is an odd function.

 For an odd function:

\(\mathop \smallint \nolimits_{ - a}^a x\;{f(x)}dx\) = 0

For a even function

\(\mathop \smallint \nolimits_{ - a}^a x\;{f(x)}dx\) = 2 × \(\mathop \smallint \nolimits_{ 0}^a x\;{f(x)}dx\)

 Now, as the function is odd

\(\mathop \smallint \nolimits_{ - 1}^1 x\;{e^{\left| x \right|}}dx\) = 0

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Important Questions from Definite Integrals

  1. What is \(\displaystyle \int_0^\pi\left(\sin ^4 x+\cos ^4 x\right) d x\) equal to?

  2. What is I equal to?

  3. What is I 1equal to?

  4. What is I 2+ I 3equal to?

  5. What is I m is equal to?

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