Math Problem Statement

Evaluate the integral \( \int \frac{dx}{\sin^2 x \cos^2 x} \).

Solution

The integral in the image is:

dxsin2xcos2x.\int \frac{dx}{\sin^2 x \cos^2 x}.

Solution:

We start by rewriting the denominator: sin2xcos2x=(sinxcosx)2.\sin^2 x \cos^2 x = (\sin x \cos x)^2.

Thus, the integral becomes: dxsin2xcos2x=dx(sinxcosx)2.\int \frac{dx}{\sin^2 x \cos^2 x} = \int \frac{dx}{(\sin x \cos x)^2}.

Next, use the double-angle identity: sin(2x)=2sinxcosx    sinxcosx=sin(2x)2.\sin(2x) = 2 \sin x \cos x \quad \implies \quad \sin x \cos x = \frac{\sin(2x)}{2}.

Substituting this into the integral: dx(sinxcosx)2=dx(sin(2x)2)2.\int \frac{dx}{(\sin x \cos x)^2} = \int \frac{dx}{\left(\frac{\sin(2x)}{2}\right)^2}.

Simplify the denominator: (sin(2x)2)2=sin2(2x)4.\left(\frac{\sin(2x)}{2}\right)^2 = \frac{\sin^2(2x)}{4}.

So the integral becomes: dxsin2(2x)4=4dxsin2(2x).\int \frac{dx}{\frac{\sin^2(2x)}{4}} = \int \frac{4 \, dx}{\sin^2(2x)}.

The reciprocal of sin2(2x)\sin^2(2x) is csc2(2x)\csc^2(2x), so: 4dxsin2(2x)=4csc2(2x)dx.\int \frac{4 \, dx}{\sin^2(2x)} = 4 \int \csc^2(2x) \, dx.

The integral of csc2(kx)\csc^2(kx) is 1kcot(kx)-\frac{1}{k} \cot(kx), so: 4csc2(2x)dx=4(12cot(2x))=2cot(2x).4 \int \csc^2(2x) \, dx = 4 \cdot \left(-\frac{1}{2} \cot(2x)\right) = -2 \cot(2x).

Thus, the solution is: 2cot(2x)+C,\boxed{-2 \cot(2x) + C}, where CC is the constant of integration.


Would you like further details or clarification?
Here are 5 related questions you can explore:

  1. How is the double-angle identity for sine derived?
  2. What is the integral of csc2(kx)\csc^2(kx) and why does it involve cot(kx)\cot(kx)?
  3. How can trigonometric integrals be simplified using substitution?
  4. What are other ways to evaluate dxsin2xcos2x\int \frac{dx}{\sin^2 x \cos^2 x}?
  5. How is the constant of integration CC important in indefinite integrals?

Tip: Always consider trigonometric identities when simplifying integrals involving sine and cosine.

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Math Problem Analysis

Mathematical Concepts

Integration
Trigonometric Identities
Definite and Indefinite Integrals

Formulas

sin^2 x cos^2 x = (sin x cos x)^2
sin(2x) = 2 sin x cos x
Integral of csc^2(kx) dx = -1/k cot(kx)

Theorems

Double-angle identity for sine: sin(2x) = 2 sin x cos x
Integration rule: ∫ csc^2(kx) dx = -1/k cot(kx)

Suitable Grade Level

Grades 11-12, Early College