Question:

$\int\limits^{\pi}_{{0}}[cot\,x]dx, [??$ denotes the greatest integer function, is equal to

Updated On: Jul 28, 2022
  • $\frac{\pi}{2}$
  • $1$
  • $-1$
  • $-\frac{\pi}{2}$
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The Correct Option is D

Solution and Explanation

Let $I=\int\limits^{\pi}_{{0}}[cot\,x]dx \,...(1)$ $=\int\limits^{\pi}_{{0}}[cot(\pi-x)]dx\int\limits^{\pi}_{{0}}--cot\,x]dx \,...(1)$ Adding (1) and (2) $2I=\int\limits^{\pi}_{{0}}[cot\,x]dx+\int\limits^{\pi}_{{0}}[cot\,x]dx=\int\limits^{\pi}_{{0}}(-1)dx\,\,\,$$\left[\because\left[x\right]+\left[-x\right]=-1 \,if\,x\notin Z=0\,if\,x\in Z\right]$ $=\left[-x\right]^{\pi}_{0}=-\pi$ $\therefore I=-\frac{\pi}{2}$
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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.