Math Problem Statement

Evaluate the limit: lim(x → 0) cos(x) / x

Solution

The image shows the limit:

limx0cos(x)x\lim_{{x \to 0}} \frac{{\cos(x)}}{x}

Solving the limit:

We need to find the value of:

limx0cos(x)x\lim_{{x \to 0}} \frac{{\cos(x)}}{x}

  1. Direct Substitution:

    • If we substitute x=0x = 0 directly, we get: cos(0)0=10\frac{{\cos(0)}}{0} = \frac{1}{0} which is undefined because division by zero is not allowed.
  2. Using L'Hopital's Rule: L'Hopital's Rule applies when we have an indeterminate form like 00\frac{0}{0}. Here, we already know direct substitution leads to undefined, so we proceed with L'Hopital's Rule:

    • First, differentiate the numerator and denominator: Numerator: ddx[cos(x)]=sin(x)\text{Numerator: } \frac{d}{dx} [\cos(x)] = -\sin(x) Denominator: ddx[x]=1\text{Denominator: } \frac{d}{dx} [x] = 1
    • Apply L'Hopital's Rule: limx0cos(x)x=limx0sin(x)1\lim_{{x \to 0}} \frac{{\cos(x)}}{x} = \lim_{{x \to 0}} \frac{{-\sin(x)}}{1}
  3. Substitute x=0x = 0 again: limx0(sin(x))=sin(0)=0\lim_{{x \to 0}} (-\sin(x)) = -\sin(0) = 0

Thus, the final answer is:

limx0cos(x)x=0\lim_{{x \to 0}} \frac{{\cos(x)}}{x} = 0

Would you like any further details or have any questions?

Here are 5 related questions to expand on this:

  1. What are the conditions for applying L'Hopital's Rule?
  2. How do we differentiate sin(x)\sin(x) and cos(x)\cos(x)?
  3. What happens to limx0sin(x)x\lim_{{x \to 0}} \frac{\sin(x)}{x}?
  4. Can L'Hopital's Rule be applied to limits approaching infinity?
  5. What other methods, besides L'Hopital's Rule, can be used to evaluate limits involving trigonometric functions?

Tip: Always check if a limit can be simplified or solved by substitution before applying more complex methods like L'Hopital's Rule.

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Math Problem Analysis

Mathematical Concepts

Limits
Trigonometry
L'Hopital's Rule

Formulas

lim(x → 0) (cos(x) / x)
L'Hopital's Rule: lim(x → 0) f(x) / g(x) = lim(x → 0) f'(x) / g'(x)

Theorems

L'Hopital's Rule

Suitable Grade Level

College Calculus