Math Problem Statement

Tìm phần chính dạng Cx^α khi x → 0 của các hàm số:

Solution

The problem you provided asks to find the main form of CxαCx^\alpha as x0x \to 0 for the following functions:

  • (a) f(x)=12x1+xf(x) = \sqrt{1 - 2x - 1 + x}
  • (b) f(x)=tan(x)sin(x)f(x) = \tan(x) - \sin(x)
  • (c) f(x)=ex2cos(x)f(x) = e^{x^2} - \cos(x)
  • (d) f(x)=32+cos(x)f(x) = \sqrt{3} - \sqrt{2 + \cos(x)}

This involves expanding each function using series expansions for small values of xx (i.e., x0x \to 0) and identifying the dominant behavior. Let's go through each one to analyze the asymptotic form.

I will start by simplifying the functions and expanding them. Let me proceed with the calculations now. sympy as sp

Define the variable

x = sp.symbols('x')

Define the functions

f_a = sp.sqrt(1 - 2*x - 1 + x) # Function (a) f_b = sp.tan(x) - sp.sin(x) # Function (b) f_c = sp.exp(x**2) - sp.cos(x) # Function (c) f_d = sp.sqrt(3) - sp.sqrt(2 + sp.cos(x)) # Function (d)

Perform series expansion at x = 0 for each function

exp_a = sp.series(f_a, x, 0, 5).simplify() exp_b = sp.series(f_b, x, 0, 5).simplify() exp_c = sp.series(f_c, x, 0, 5).simplify() exp_d = sp.series(f_d, x, 0, 5).simplify()

exp_a, exp_b, exp_c, exp_dHere are the results of the series expansions for each function as x0x \to 0:

  1. For f(x)=12x1+xf(x) = \sqrt{1 - 2x - 1 + x}: f(x)=ixf(x) = i\sqrt{x} This function involves an imaginary term, suggesting it has a complex nature for small xx.

  2. For f(x)=tan(x)sin(x)f(x) = \tan(x) - \sin(x): f(x)=x32+O(x5)f(x) = \frac{x^3}{2} + O(x^5) The dominant term is x32\frac{x^3}{2}, so the function behaves like CxαCx^\alpha with α=3\alpha = 3.

  3. For f(x)=ex2cos(x)f(x) = e^{x^2} - \cos(x): f(x)=3x22+11x424+O(x5)f(x) = \frac{3x^2}{2} + \frac{11x^4}{24} + O(x^5) The dominant term is 3x22\frac{3x^2}{2}, so the function behaves like CxαCx^\alpha with α=2\alpha = 2.

  4. For f(x)=32+cos(x)f(x) = \sqrt{3} - \sqrt{2 + \cos(x)}: f(x)=3x2123x4288+O(x5)f(x) = \frac{\sqrt{3}x^2}{12} - \frac{\sqrt{3}x^4}{288} + O(x^5) The dominant term is 3x212\frac{\sqrt{3}x^2}{12}, so the function behaves like CxαCx^\alpha with α=2\alpha = 2.

Summary of results:

  • (a) f(x)=12x1+xf(x) = \sqrt{1 - 2x - 1 + x} tends to an imaginary term ixi\sqrt{x}.
  • (b) f(x)=tan(x)sin(x)f(x) = \tan(x) - \sin(x) behaves like x3x^3.
  • (c) f(x)=ex2cos(x)f(x) = e^{x^2} - \cos(x) behaves like x2x^2.
  • (d) f(x)=32+cos(x)f(x) = \sqrt{3} - \sqrt{2 + \cos(x)} behaves like x2x^2.

Would you like further clarification on any part of the solution?

Related questions to explore:

  1. How does the behavior of tan(x)sin(x)\tan(x) - \sin(x) change as x0x \to 0?
  2. What is the significance of the imaginary term in function (a)?
  3. Can we generalize the form CxαCx^\alpha for more complicated functions?
  4. How do higher-order terms in the series affect the asymptotic behavior of these functions?
  5. What is the connection between Taylor series and asymptotic analysis?

Tip: The series expansion helps identify the most significant terms for small values of xx, which are critical for understanding the behavior near zero.

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Math Problem Analysis

Mathematical Concepts

Asymptotic analysis
Taylor series expansion
Limits
Behavior near zero

Formulas

f(x) ≈ Cx^α as x → 0
Taylor series: f(x) = f(0) + f'(0)x + f''(0)x^2/2! + ...

Theorems

Taylor's Theorem
Asymptotic behavior analysis

Suitable Grade Level

University level or advanced high school