Math Problem Statement

Solve the integrals: 1. ∫ dx / √(25 + 4x²) 2. ∫ 1 / (x√(x⁴ - 1)) dx

Solution

The uploaded image contains two integrals that need to be solved:

  1. dx25+4x2\int \frac{dx}{\sqrt{25 + 4x^2}}
  2. 1xx41dx\int \frac{1}{x\sqrt{x^4 - 1}} dx

Let me solve these integrals step by step.


1. Solve dx25+4x2\int \frac{dx}{\sqrt{25 + 4x^2}}:

We use the substitution method here:

  • Let x=52tanθx = \frac{5}{2} \tan \theta, so dx=52sec2θdθdx = \frac{5}{2} \sec^2 \theta d\theta.
  • Then, 25+4x2=25+4(52tanθ)2=25sec2θ25 + 4x^2 = 25 + 4\left(\frac{5}{2}\tan\theta\right)^2 = 25\sec^2\theta.

Substitute: dx25+4x2=52sec2θdθ25sec2θ=52sec2θ5secθdθ=12secθdθ\int \frac{dx}{\sqrt{25 + 4x^2}} = \int \frac{\frac{5}{2}\sec^2\theta d\theta}{\sqrt{25\sec^2\theta}} = \int \frac{\frac{5}{2}\sec^2\theta}{5\sec\theta} d\theta = \int \frac{1}{2} \sec\theta d\theta

The integral of secθ\sec\theta is lnsecθ+tanθ+C\ln|\sec\theta + \tan\theta| + C. Thus: dx25+4x2=12lnsecθ+tanθ+C\int \frac{dx}{\sqrt{25 + 4x^2}} = \frac{1}{2} \ln|\sec\theta + \tan\theta| + C

Rewriting in terms of xx:

  • Since x=52tanθx = \frac{5}{2}\tan\theta, we have tanθ=2x5\tan\theta = \frac{2x}{5} and secθ=1+tan2θ=1+(2x5)2=25+4x25\sec\theta = \sqrt{1 + \tan^2\theta} = \sqrt{1 + \left(\frac{2x}{5}\right)^2} = \frac{\sqrt{25 + 4x^2}}{5}.

Thus, the solution becomes: dx25+4x2=12ln25+4x25+2x5+C\int \frac{dx}{\sqrt{25 + 4x^2}} = \frac{1}{2} \ln\left|\frac{\sqrt{25 + 4x^2}}{5} + \frac{2x}{5}\right| + C


2. Solve 1xx41dx\int \frac{1}{x\sqrt{x^4 - 1}} dx:

Here, we use the substitution x2=secux^2 = \sec u, so dx=secutanu2secudu=secutanu2x2dudx = \frac{\sec u \tan u}{2\sqrt{\sec u}} du = \frac{\sec u \tan u}{2\sqrt{x^2}} du.

For x41=(secu)21=tan2ux^4 - 1 = (\sec u)^2 - 1 = \tan^2 u, the integral simplifies after substitution: Let me calculate step by step and simplify furtherimport sympy as sp

Defining variables

x = sp.symbols('x')

First integral

integral_1 = sp.integrate(1 / sp.sqrt(25 + 4 * x**2), x)

Second integral

integral_2 = sp.integrate(1 / (x * sp.sqrt(x**4 - 1)), x)

integral_1, integral_2(asinh(2x/5)/2, Piecewise((Iacosh(x**(-2))/2, 1/Abs(x4) > 1), (-asin(x(-2))/2, True)))(asinh(2x/5)/2, Piecewise((Iacosh(x**(-2))/2, 1/Abs(x4) > 1), (-asin(x(-2))/2, True)))successHere are the results for the given integrals:

  1. For dx25+4x2\int \frac{dx}{\sqrt{25 + 4x^2}}: 12sinh1(2x5)+C\frac{1}{2} \sinh^{-1}\left(\frac{2x}{5}\right) + C

  2. For 1xx41dx\int \frac{1}{x\sqrt{x^4 - 1}} dx:

    \frac{i}{2} \cosh^{-1}\left(x^{-2}\right) + C & \text{if } \frac{1}{|x^4|} > 1 \\ -\frac{1}{2} \sin^{-1}\left(x^{-2}\right) + C & \text{otherwise} \end{cases}$$

These are the simplified results for the integrals.

Would you like detailed steps for the second integral or clarification on the inverse hyperbolic and trigonometric functions?


Expanding Questions:

  1. Can these results be transformed into other forms for specific applications?
  2. How do hyperbolic and trigonometric substitutions help in solving integrals?
  3. Can we numerically approximate these integrals for specific xx values?
  4. What are some practical scenarios where such integrals arise?
  5. How can substitution choices impact the complexity of solving an integral?

Tip: When facing challenging integrals, look for symmetry, standard forms, or substitution methods that simplify radicals or trigonometric expressions.

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Trigonometric Substitution
Inverse Trigonometric Functions
Hyperbolic Functions

Formulas

Substitution: x = a tan(θ), dx = a sec²(θ) dθ
Integration of sec(θ): ∫ sec(θ) dθ = ln|sec(θ) + tan(θ)| + C
Hyperbolic substitution: x² = sec(u), dx = (sec(u) tan(u))/sqrt(sec(u)) du

Theorems

Pythagorean Identities for trigonometric simplifications
Hyperbolic and inverse hyperbolic function properties

Suitable Grade Level

Undergraduate Level