Question:medium

If \(\int\frac{\csc^{2}x-2010}{\cos^{2010}x}dx=-\frac{f(x)}{(g(x))^{2010}}+c\), where \(f\left(\frac{\pi}{4}\right)=1\), then the number of solutions of the equation \(\frac{f(x)}{g(x)}=\{x\}\) in \([0,2\pi]\) is/are (where \(\{\cdot\}\) represents fractional part function):

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Whenever an integration problem contains a large year number (like 2010), don't panic! It is a sign that the problem is designed around a clean cancellation pattern or power derivative rule where the large number acts as a constant multiplier.
Updated On: May 28, 2026
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The Correct Option is C

Solution and Explanation

Step 1: Understanding the Concept:
This problem involves solving a complex-looking integral by identifying a derivative of a quotient and then analyzing the resulting trigonometric equation with a fractional part function.
Step 2: Key Formula or Approach:
Consider the derivative of \( \frac{\cot x}{(\cos x)^n} \).
\[ \frac{d}{dx} \left( \frac{\cot x}{(\cos x)^{2010}} \right) = \frac{(-\csc^2 x)(\cos x)^{2010} - (\cot x)(2010)(\cos x)^{2009}(-\sin x)}{(\cos x)^{4020}} \] Simplify the second term in the numerator: \( \cot x \cdot \sin x = \cos x \).
\[ = \frac{-\csc^2 x (\cos x)^{2010} + 2010 (\cos x)^{2010}}{(\cos x)^{4020}} = \frac{-\csc^2 x + 2010}{(\cos x)^{2010}} \] Step 3: Detailed Explanation:
The integral is: \[ \int \frac{\csc^2 x - 2010}{\cos^{2010} x} dx = - \int \frac{-\csc^2 x + 2010}{\cos^{2010} x} dx \] From our derivative calculation: \[ = - \left( \frac{\cot x}{(\cos x)^{2010}} \right) + c \] Comparing this with the given form \( -\frac{f(x)}{(g(x))^{2010}} \), we identify: - \( f(x) = \cot x \)
- \( g(x) = \cos x \)
Check condition: \( f(\pi/4) = \cot(\pi/4) = 1 \). Correct.
Now we solve the equation: \[ \frac{f(x)}{g(x)} = \{x\} \implies \frac{\cot x}{\cos x} = \{x\} \implies \frac{\cos x}{\sin x \cos x} = \{x\} \implies \csc x = \{x\} \] Analyze the range: - For any real \( x \), \( \{x\} \in [0, 1) \).
- The function \( \csc x \) has a range \( (-\infty, -1] \cup [1, \infty) \).
There is no overlap between the set \( [0, 1) \) and the set \( (-\infty, -1] \cup [1, \infty) \).
Step 4: Final Answer:
Since the range of the Left-Hand Side and Right-Hand Side are disjoint, there are no solutions. Thus, the number of solutions is 0.
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