Math Problem Statement

∫ (1 + sec^3(x)) / cot(x) dx

Solution

The integral shown is:

1+sec3xcotxdx\int \frac{1 + \sec^3 x}{\cot x} \, dx

To solve this integral, we can first simplify it by expressing cotx\cot x in terms of sinx\sin x and cosx\cos x, and then use substitution techniques if necessary.

Step 1: Express cotx\cot x in terms of sine and cosine.

cotx=cosxsinx\cot x = \frac{\cos x}{\sin x}

Now the integral becomes: (1+sec3x)cosxsinxdx=(1+sec3x)sinxcosxdx\int \frac{(1 + \sec^3 x)}{\frac{\cos x}{\sin x}} \, dx = \int \frac{(1 + \sec^3 x) \sin x}{\cos x} \, dx

Step 2: Express sec3x\sec^3 x in terms of cosx\cos x.

Recall that secx=1cosx\sec x = \frac{1}{\cos x}, so: sec3x=1cos3x\sec^3 x = \frac{1}{\cos^3 x}

Substitute this into the integral: (1+1cos3x)sinxcosxdx=(sinxcosx+sinxcos4x)dx\int \frac{(1 + \frac{1}{\cos^3 x}) \sin x}{\cos x} \, dx = \int \left( \frac{\sin x}{\cos x} + \frac{\sin x}{\cos^4 x} \right) dx

Step 3: Split the integral.

Now we have two simpler integrals to deal with: sinxcosxdx+sinxcos4xdx\int \frac{\sin x}{\cos x} \, dx + \int \frac{\sin x}{\cos^4 x} \, dx

First integral:

sinxcosxdx=tanxdx=lnsecx+C1\int \frac{\sin x}{\cos x} \, dx = \int \tan x \, dx = \ln |\sec x| + C_1

Second integral:

To handle the second integral, we can use the substitution u=cosxu = \cos x, so du=sinxdxdu = -\sin x \, dx, transforming the integral into: 1u4du=13u3+C2=13cos3x+C2-\int \frac{1}{u^4} \, du = \frac{1}{3u^3} + C_2 = \frac{1}{3\cos^3 x} + C_2

Step 4: Combine the results.

Now combine the results from both integrals: lnsecx13cos3x+C\ln |\sec x| - \frac{1}{3\cos^3 x} + C

Thus, the solution to the integral is:

lnsecx13cos3x+C\ln |\sec x| - \frac{1}{3\cos^3 x} + C

Would you like any further clarification or details on any part of this solution?

Here are 5 related questions to explore further:

  1. How do you approach integrals involving trigonometric identities?
  2. What are common trigonometric substitutions in integrals?
  3. How can we integrate secnx\sec^n x for different powers of nn?
  4. What is the role of logarithmic functions in trigonometric integrals?
  5. Can you derive the integral of tanx\tan x without using substitution?

Tip: When solving integrals involving trigonometric functions, it's helpful to recall basic identities and be comfortable using substitutions for simplification.

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Math Problem Analysis

Mathematical Concepts

Trigonometric Integration
Substitution Method

Formulas

cot(x) = cos(x) / sin(x)
sec^3(x) = 1 / cos^3(x)
∫ tan(x) dx = ln |sec(x)| + C
Substitution: u = cos(x), du = -sin(x) dx

Theorems

Fundamental Theorem of Calculus
Trigonometric Identities

Suitable Grade Level

Undergraduate Calculus