Question:

$\int\limits^{-\pi/2}_{{-3\pi/2}}$$\left[\left(x+\pi\right)^{3}+cos^{2} \left(x+3\pi\right)\right]dx$ is equal to :

Updated On: Jul 27, 2022
  • $\left(\frac{\pi^{4}}{32}\right)+\left(\frac{\pi}{2}\right)$
  • $\frac{\pi}{2}$
  • $\left(\frac{\pi}{4}\right)-1$
  • $\frac{\pi^{4}}{32}$
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The Correct Option is B

Solution and Explanation

Let $\int\limits^{-\pi/2}_{{-3\pi/2}}$$\left[\left(x+\pi\right)^{3}+cos^{2} \left(x+3\pi\right)\right]dx ...(i)$ and $I=\int\limits^{-\pi/2}_{{-3\pi/2}}$$\left[\left(-\frac{\pi}{2}-\frac{3\pi}{2}-x+\pi\right)^{3}+cos^{2}\left(-\frac{\pi}{2}-\frac{3\pi}{2}-x+3\pi\right)\right]dx$ $\Rightarrow $ $I=\int\limits^{-\pi/2}_{{-3\pi/2}}$$\left[-\left(x+\pi\right)^{3}+cos^{2}\left(\pi-x\right)\right]dx ...\left(ii\right)$ On adding Eqs. (i) and (ii), we get $2I=\int\limits^{-\pi/2}_{{-3\pi/2}}$$2\,cos^{2}\,x\,dx$ $=\int\limits^{-\pi/2}_{{-3\pi/2}}$$\left(1+cos\,2x\right)dx$ $=\left[x+\frac{sin\,2x}{2}\right]^{-\pi/2}_{_{_{-3\pi/2}}}$ $=-\frac{\pi}{2}+\frac{3\pi}{2}=\pi$ $\Rightarrow I=\frac{\pi}{2}$
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Concepts Used:

Integral

The representation of the area of a region under a curve is called to be as integral. The actual value of an integral can be acquired (approximately) by drawing rectangles.

  • The definite integral of a function can be shown as the area of the region bounded by its graph of the given function between two points in the line.
  • The area of a region is found by splitting it into thin vertical rectangles and applying the lower and the upper limits, the area of the region is summarized.
  • An integral of a function over an interval on which the integral is described.

Also, F(x) is known to be a Newton-Leibnitz integral or antiderivative or primitive of a function f(x) on an interval I.

F'(x) = f(x)

For every value of x = I.

Types of Integrals:

Integral calculus helps to resolve two major types of problems:

  1. The problem of getting a function if its derivative is given.
  2. The problem of getting the area bounded by the graph of a function under given situations.