Math Problem Statement

solve using trig sub

Solve the integral \(\int \frac{dx}{(1 - x^2)^{3/2}}\) using trigonometric substitution.

Solution

To solve the integral dx(1x2)3/2\int \frac{dx}{(1 - x^2)^{3/2}} using trigonometric substitution, we follow these steps:

Step 1: Trigonometric Substitution

We use the substitution: x=sinθorx=cosθx = \sin \theta \quad \text{or} \quad x = \cos \theta For this integral, we choose x=sinθx = \sin \theta, hence: dx=cosθdθdx = \cos \theta \, d\theta

Step 2: Rewrite the Integral

Substitute x=sinθx = \sin \theta and dx=cosθdθdx = \cos \theta \, d\theta into the integral: dx(1x2)3/2=cosθdθ(1sin2θ)3/2\int \frac{dx}{(1 - x^2)^{3/2}} = \int \frac{\cos \theta \, d\theta}{(1 - \sin^2 \theta)^{3/2}}

Step 3: Simplify the Denominator

Using the identity 1sin2θ=cos2θ1 - \sin^2 \theta = \cos^2 \theta, we get: cosθdθ(cos2θ)3/2=cosθdθcos3θ\int \frac{\cos \theta \, d\theta}{(\cos^2 \theta)^{3/2}} = \int \frac{\cos \theta \, d\theta}{\cos^3 \theta} Simplify this expression: 1cos2θdθ=sec2θdθ\int \frac{1}{\cos^2 \theta} \, d\theta = \int \sec^2 \theta \, d\theta

Step 4: Integrate

The integral of sec2θ\sec^2 \theta is: sec2θdθ=tanθ+C\int \sec^2 \theta \, d\theta = \tan \theta + C

Step 5: Back-Substitution

Recall the substitution x=sinθx = \sin \theta, so: tanθ=sinθcosθ=x1x2\tan \theta = \frac{\sin \theta}{\cos \theta} = \frac{x}{\sqrt{1 - x^2}}

Thus, the final solution is: dx(1x2)3/2=x1x2+C\int \frac{dx}{(1 - x^2)^{3/2}} = \frac{x}{\sqrt{1 - x^2}} + C

Would you like further details or have any questions?

Here are 5 related questions for further practice:

  1. How would you solve the integral dx(1x2)1/2\int \frac{dx}{(1 - x^2)^{1/2}} using trigonometric substitution?
  2. Can you find the integral xdx(1x2)3/2\int \frac{x \, dx}{(1 - x^2)^{3/2}} using the same substitution?
  3. How would you solve dx(4x2)3/2\int \frac{dx}{(4 - x^2)^{3/2}} with trigonometric substitution?
  4. What is the result of dx(1+x2)3/2\int \frac{dx}{(1 + x^2)^{3/2}} using a different trigonometric substitution?
  5. How would the substitution differ for dx(x21)3/2\int \frac{dx}{(x^2 - 1)^{3/2}}?

Tip: Always remember to check if the substitution fits the integral's form to simplify the expression before solving.

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Trigonometric Substitution

Formulas

\(x = \sin \theta\)
\(dx = \cos \theta \, d\theta\)
\(1 - \sin^2 \theta = \cos^2 \theta\)
\(\int \sec^2 \theta \, d\theta = \tan \theta + C\)

Theorems

Trigonometric substitution
Pythagorean identities

Suitable Grade Level

College Calculus