Math Problem Statement

کامل و خلاصه حل کن

کامل و خلاصه حل کن

Solution

I see you've uploaded an image of two integrals that need to be solved. I'll provide solutions for both. Let’s go step by step:


(الف)

01ln(x)1xdx\int_0^1 \frac{\ln(x)}{\sqrt{1 - x}} \, dx

Solution:

We will solve this using substitution:

  1. Let x=sin2(t)x = \sin^2(t), so dx=2sin(t)cos(t)dt=sin(2t)dtdx = 2\sin(t)\cos(t) \, dt = \sin(2t) \, dt.
  2. The limits transform as follows:
    • When x=0x = 0, t=0t = 0,
    • When x=1x = 1, t=π2t = \frac{\pi}{2}.
  3. Substitute into the integral: 01ln(x)1xdx=0π2ln(sin2(t))cos(t)sin(2t)dt.\int_0^1 \frac{\ln(x)}{\sqrt{1 - x}} \, dx = \int_0^{\frac{\pi}{2}} \frac{\ln(\sin^2(t))}{\cos(t)} \cdot \sin(2t) \, dt.
  4. Simplify using ln(sin2(t))=2ln(sin(t))\ln(\sin^2(t)) = 2\ln(\sin(t)) and sin(2t)=2sin(t)cos(t)\sin(2t) = 2\sin(t)\cos(t): 0π2ln(sin2(t))cos(t)sin(2t)dt=20π2ln(sin(t))2sin(t)dt.\int_0^{\frac{\pi}{2}} \frac{\ln(\sin^2(t))}{\cos(t)} \cdot \sin(2t) \, dt = 2\int_0^{\frac{\pi}{2}} \ln(\sin(t)) \cdot 2\sin(t) \, dt. This reduces to: 40π2ln(sin(t))dt.4\int_0^{\frac{\pi}{2}} \ln(\sin(t)) \, dt.

Result:

A known result is that: 0π2ln(sin(t))dt=π2ln(2).\int_0^{\frac{\pi}{2}} \ln(\sin(t)) \, dt = -\frac{\pi}{2} \ln(2). Thus: 01ln(x)1xdx=4(π2ln(2))=2πln(2).\int_0^1 \frac{\ln(x)}{\sqrt{1 - x}} \, dx = 4 \left(-\frac{\pi}{2} \ln(2)\right) = -2\pi \ln(2).


(ب)

1eln(x)x(1+(ln(x))2)dx\int_1^e \frac{\ln(x)}{x \left(1 + (\ln(x))^2\right)} \, dx

Solution:

We solve using substitution:

  1. Let u=ln(x)u = \ln(x), so du=1xdxdu = \frac{1}{x} \, dx.
  2. The limits transform as follows:
    • When x=1x = 1, u=ln(1)=0u = \ln(1) = 0,
    • When x=ex = e, u=ln(e)=1u = \ln(e) = 1.
  3. Substitute into the integral: 1eln(x)x(1+(ln(x))2)dx=01u1+u2du.\int_1^e \frac{\ln(x)}{x \left(1 + (\ln(x))^2\right)} \, dx = \int_0^1 \frac{u}{1 + u^2} \, du.

Simplify:

The integral becomes: 01u1+u2du.\int_0^1 \frac{u}{1 + u^2} \, du. Using substitution v=1+u2v = 1 + u^2, dv=2ududv = 2u \, du, the limits transform as:

  • When u=0u = 0, v=1v = 1,
  • When u=1u = 1, v=2v = 2.

The integral becomes: 01u1+u2du=12121vdv.\int_0^1 \frac{u}{1 + u^2} \, du = \frac{1}{2} \int_1^2 \frac{1}{v} \, dv.

Solve:

12121vdv=12ln(v)12=12(ln(2)ln(1)).\frac{1}{2} \int_1^2 \frac{1}{v} \, dv = \frac{1}{2} \ln(v) \bigg|_1^2 = \frac{1}{2} \left(\ln(2) - \ln(1)\right). Since ln(1)=0\ln(1) = 0, the result is: 12ln(2).\frac{1}{2} \ln(2).


Final Answers:

  1. (الف): 01ln(x)1xdx=2πln(2).\int_0^1 \frac{\ln(x)}{\sqrt{1 - x}} \, dx = -2\pi \ln(2).
  2. (ب): 1eln(x)x(1+(ln(x))2)dx=12ln(2).\int_1^e \frac{\ln(x)}{x \left(1 + (\ln(x))^2\right)} \, dx = \frac{1}{2} \ln(2).

Would you like further clarification on any step or a more detailed explanation?

Related Questions:

  1. How can substitution techniques simplify challenging integrals?
  2. What are some common integral results involving logarithmic functions?
  3. How is symmetry used in definite integrals?
  4. Can we solve the first integral without substitution?
  5. Why is 0π2ln(sin(t))dt=π2ln(2)\int_0^{\frac{\pi}{2}} \ln(\sin(t)) \, dt = -\frac{\pi}{2} \ln(2) a standard result?

Tip:

When solving integrals, recognize patterns that align with standard results to save time and effort.

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Math Problem Analysis

Mathematical Concepts

Definite Integrals
Logarithmic Functions
Trigonometric Substitution

Formulas

\( \ln(\sin^2(t)) = 2\ln(\sin(t)) \)
\( \sin(2t) = 2\sin(t)\cos(t) \)
\( \int \frac{u}{1 + u^2} du \to \text{Logarithmic Simplification} \)

Theorems

Known Result: \( \int_0^{\frac{\pi}{2}} \ln(\sin(t)) dt = -\frac{\pi}{2} \ln(2) \)
Substitution Rule for Integration

Suitable Grade Level

University-level Calculus