Math Problem Statement

∫sech (ln(x)) dx

Solution

To solve the integral sech(ln(x))dx\int \text{sech}(\ln(x)) \, dx, we can use a substitution method.

Let u=ln(x)u = \ln(x). Then, du=1xdxdu = \frac{1}{x} dx or equivalently dx=xdu=eududx = x \, du = e^u \, du.

Now, we rewrite the integral in terms of uu:

sech(ln(x))dx=sech(u)eudu\int \text{sech}(\ln(x)) \, dx = \int \text{sech}(u) \cdot e^u \, du

We recognize that sech(u)=2eu+eu\text{sech}(u) = \frac{2}{e^u + e^{-u}}, so the integral becomes:

2eueu+eudu\int \frac{2 e^u}{e^u + e^{-u}} \, du

Simplify the integrand:

2eueu+1eudu=2eue2u+1du\int \frac{2 e^u}{e^u + \frac{1}{e^u}} \, du = \int \frac{2 e^u}{e^{2u} + 1} \, du

Notice that 2eue2u+1\frac{2 e^u}{e^{2u} + 1} can be integrated directly as it matches the derivative of the arctangent function:

2eue2u+1du=211+e2udu\int \frac{2 e^u}{e^{2u} + 1} \, du = 2 \int \frac{1}{1 + e^{-2u}} \, du

This integral can be recognized as:

211+e2udu=2arctan(eu)+C2 \int \frac{1}{1 + e^{-2u}} \, du = 2 \arctan(e^u) + C

Now, substituting back u=ln(x)u = \ln(x):

2arctan(eln(x))+C=2arctan(x)+C2 \arctan(e^{\ln(x)}) + C = 2 \arctan(x) + C

Thus, the solution to the integral sech(ln(x))dx\int \text{sech}(\ln(x)) \, dx is:

2arctan(x)+C\boxed{2 \arctan(x) + C}

Would you like more details or have any questions?

Here are five more questions you might consider:

  1. How do you solve 1xln(x)dx\int \frac{1}{x \ln(x)} \, dx?
  2. What is the integral of ex2dxe^{x^2} \, dx?
  3. Can you explain the method of partial fractions?
  4. How do you find the derivative of tan1(x)\tan^{-1}(x)?
  5. What is the integral of sin2(x)dx\sin^2(x) \, dx?

Tip: When dealing with integrals involving logarithmic or exponential functions, substitution is often a helpful method to simplify the integral.

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Math Problem Analysis

Mathematical Concepts

Integration
Hyperbolic Functions
Substitution Method

Formulas

Integral of sech(u)

Theorems

Integral substitution theorem
Arctangent derivative

Suitable Grade Level

Advanced College Level