Math Problem Statement

integrate 1/(16-t^2)^3/2

Solution

To solve the integral:

I=1(16t2)3/2dtI = \int \frac{1}{(16 - t^2)^{3/2}} \, dt

We can use a standard trigonometric substitution, which is effective for integrals of the form 1(a2x2)3/2\frac{1}{(a^2 - x^2)^{3/2}}.

Step 1: Apply a trigonometric substitution.

Let t=4sinθt = 4 \sin \theta. This gives:

  • dt=4cosθdθdt = 4 \cos \theta \, d\theta
  • 16t2=1616sin2θ=16cos2θ16 - t^2 = 16 - 16\sin^2 \theta = 16 \cos^2 \theta

Thus, the integral becomes:

I=1(16cos2θ)3/24cosθdθI = \int \frac{1}{(16 \cos^2 \theta)^{3/2}} \cdot 4 \cos \theta \, d\theta

Simplifying the powers:

I=4cosθ163/2cos3θdθ=4163/2cos2θdθI = \int \frac{4 \cos \theta}{16^{3/2} \cos^3 \theta} \, d\theta = \int \frac{4}{16^{3/2} \cos^2 \theta} \, d\theta

Since 163/2=6416^{3/2} = 64, the integral becomes:

I=164sec2θdθI = \frac{1}{64} \int \sec^2 \theta \, d\theta

Step 2: Integrate.

We know that the integral of sec2θ\sec^2 \theta is tanθ\tan \theta. So:

I=164tanθ+CI = \frac{1}{64} \tan \theta + C

Step 3: Substitute back in terms of tt.

Since t=4sinθt = 4 \sin \theta, we can find tanθ\tan \theta as:

sinθ=t4,cosθ=1sin2θ=1(t4)2=16t24\sin \theta = \frac{t}{4}, \quad \cos \theta = \sqrt{1 - \sin^2 \theta} = \sqrt{1 - \left( \frac{t}{4} \right)^2} = \frac{\sqrt{16 - t^2}}{4}

Thus:

tanθ=sinθcosθ=t16t2\tan \theta = \frac{\sin \theta}{\cos \theta} = \frac{t}{\sqrt{16 - t^2}}

Therefore, the solution to the integral is:

I=164t16t2+CI = \frac{1}{64} \cdot \frac{t}{\sqrt{16 - t^2}} + C

Final Answer:

1(16t2)3/2dt=t6416t2+C\int \frac{1}{(16 - t^2)^{3/2}} \, dt = \frac{t}{64 \sqrt{16 - t^2}} + C

Let me know if you'd like more details or have any further questions!


Here are some related questions you might find interesting:

  1. How does trigonometric substitution work for integrals of the form 1(a2x2)3/2dx\int \frac{1}{(a^2 - x^2)^{3/2}} \, dx?
  2. What other substitution methods could be applied to integrals involving square roots?
  3. How do we handle integrals of rational functions like 1(x2a2)3/2\frac{1}{(x^2 - a^2)^{3/2}}?
  4. Can the result of this integral be generalized for other powers besides 32\frac{3}{2}?
  5. What is the role of the identity sec2θ=1+tan2θ\sec^2 \theta = 1 + \tan^2 \theta in simplifying trigonometric integrals?

Tip: When dealing with integrals involving square roots of quadratic expressions, always consider a trigonometric substitution, as it often simplifies the integral significantly.

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Math Problem Analysis

Mathematical Concepts

Integration
Trigonometric Substitution
Calculus

Formulas

Trigonometric Substitution: t = a sin(θ)
Integral of sec^2(θ) = tan(θ)

Theorems

Trigonometric Substitution Theorem
Basic Integral of sec^2(θ)

Suitable Grade Level

Grades 11-12