Find each of the following limits: (1) lim x→2 of (sqrt(x) - 2) / (x - 2); (2) lim x→0 of (sin x) / x; (3) lim x→3 of (x^2 - 9) / (x - 3); (4) lim x→π of (cos x); (5) lim x→4 of (x... Find each of the following limits: (1) lim x→2 of (sqrt(x) - 2) / (x - 2); (2) lim x→0 of (sin x) / x; (3) lim x→3 of (x^2 - 9) / (x - 3); (4) lim x→π of (cos x); (5) lim x→4 of (x^2 - 16) / (x - 4).

Question image

Understand the Problem

The question involves finding the limits of various functions, which requires applying limit laws and potentially evaluating limits as they approach specific values.

Answer

1. $0$ 2. $14$ 3. $6$ 4. $\frac{1}{4}$ 5. $1$ 6. $2$ 7. $0$ 8. $\frac{1}{2\sqrt{3}}$
Answer for screen readers
  1. $0$
  2. $14$
  3. $6$
  4. $\frac{1}{4}$
  5. $1$
  6. $2$
  7. $0$
  8. $\frac{1}{2\sqrt{3}}$

Steps to Solve

  1. Evaluate the first limit: $\lim_{x \to 2} (x^2 - 4)$
    Substitute $x$ with $2$ in the expression:
    $$ \lim_{x \to 2} (x^2 - 4) = 2^2 - 4 = 4 - 4 = 0 $$

  2. Evaluate the second limit: $\lim_{x \to 7} \frac{x^2 - 49}{x - 7}$
    This expression is of the form $\frac{0}{0}$. Factor the numerator:
    $$ \lim_{x \to 7} \frac{(x - 7)(x + 7)}{x - 7} = \lim_{x \to 7} (x + 7) = 7 + 7 = 14 $$

  3. Evaluate the third limit: $\lim_{x \to 3} \frac{x^2 - 9}{x - 3}$
    This is also of the form $\frac{0}{0}$. Factor the numerator:
    $$ \lim_{x \to 3} \frac{(x - 3)(x + 3)}{x - 3} = \lim_{x \to 3} (x + 3) = 3 + 3 = 6 $$

  4. Evaluate the fourth limit: $\lim_{x \to 4} \frac{\sqrt{x} - 2}{x - 4}$
    This limit also results in $\frac{0}{0}$. Multiply by the conjugate:
    $$ \lim_{x \to 4} \frac{(\sqrt{x} - 2)(\sqrt{x} + 2)}{(x - 4)(\sqrt{x} + 2)} = \lim_{x \to 4} \frac{x - 4}{(x - 4)(\sqrt{x} + 2)} = \lim_{x \to 4} \frac{1}{\sqrt{x} + 2} = \frac{1}{2 + 2} = \frac{1}{4} $$

  5. Evaluate the fifth limit: $\lim_{x \to 0} \frac{\sin x}{x}$
    A well-known limit:
    $$ \lim_{x \to 0} \frac{\sin x}{x} = 1 $$

  6. Evaluate the sixth limit: $\lim_{x \to 0^+} \frac{1 - \cos x}{x^2}$
    Using the limit property:
    $$ \lim_{x \to 0} \frac{1 - \cos x}{x^2} = \lim_{x \to 0} \frac{0}{0} = \lim_{x \to 0} \frac{\sin^2(x/2)}{(x^2/4)} = \lim_{x \to 0} \frac{4 \sin^2(x/2)}{x^2} = 2 $$

  7. Evaluate the seventh limit: $\lim_{x \to 0} \frac{x}{\sqrt{x^2 + 1}}$
    Substituting $x$ gives:
    $$ \lim_{x \to 0} \frac{0}{\sqrt{0^2 + 1}} = 0 $$

  8. Evaluate the eighth limit: $\lim_{x \to 3} \frac{\sqrt{x} - \sqrt{3}}{x - 3}$
    Using the conjugate:
    $$ \lim_{x \to 3} \frac{(\sqrt{x} - \sqrt{3})(\sqrt{x} + \sqrt{3})}{(x - 3)(\sqrt{x} + \sqrt{3})} = \lim_{x \to 3} \frac{x - 3}{(x - 3)(\sqrt{x} + \sqrt{3})} = \frac{1}{\sqrt{3} + \sqrt{3}} = \frac{1}{2\sqrt{3}} $$

  1. $0$
  2. $14$
  3. $6$
  4. $\frac{1}{4}$
  5. $1$
  6. $2$
  7. $0$
  8. $\frac{1}{2\sqrt{3}}$

More Information

These calculations show how to evaluate limits using direct substitution, factoring, and other algebraic techniques. Understanding these limit laws is essential for calculus.

Tips

  • Not recognizing forms like $\frac{0}{0}$ and attempting to substitute directly.
  • Forgetting to simplify expressions before evaluating limits.
  • Misapplying trigonometric limit properties.

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