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find the limit. 61) $lim_{x ightarrow(-2)^-}\frac{1}{x + 2}$ 62) $lim_{…

Question

find the limit.

  1. $lim_{x

ightarrow(-2)^-}\frac{1}{x + 2}$

  1. $lim_{x

ightarrow(-2)^+}\frac{1}{x + 2}$

  1. $lim_{x

ightarrow - 2}\frac{1}{x + 2}$

  1. $lim_{x

ightarrow0}\frac{1}{x^{2/3}}$

  1. $lim_{x

ightarrow(pi/2)^+}\tan x$

  1. $lim_{x

ightarrow(-pi/2)^-}sec x$

  1. $lim_{x

ightarrow0^+}(1+csc x)$

  1. $lim_{x

ightarrow0}(1 - cot x)$

Explanation:

61)

Step1: Analyze left - hand limit

As \(x\to(- 2)^{-}\), let \(x=-2 - h\) where \(h\to0^{+}\). Then \(\frac{1}{x + 2}=\frac{1}{-2 - h+2}=-\frac{1}{h}\). As \(h\to0^{+}\), \(\lim_{x\to(-2)^{-}}\frac{1}{x + 2}=-\infty\).

62)

Step1: Analyze right - hand limit

As \(x\to(-2)^{+}\), let \(x=-2 + h\) where \(h\to0^{+}\). Then \(\frac{1}{x + 2}=\frac{1}{-2 + h+2}=\frac{1}{h}\). As \(h\to0^{+}\), \(\lim_{x\to(-2)^{+}}\frac{1}{x + 2}=\infty\).

63)

Step1: Check one - sided limits

Since \(\lim_{x\to(-2)^{-}}\frac{1}{x + 2}=-\infty\) and \(\lim_{x\to(-2)^{+}}\frac{1}{x + 2}=\infty\), the two - sided limit \(\lim_{x\to - 2}\frac{1}{x + 2}\) does not exist.

64)

Step1: Analyze limit as \(x\to0\)

As \(x\to0\), if \(x\to0^{+}\), \(\frac{1}{x^{2/3}}=\frac{1}{\sqrt[3]{x^{2}}}\to+\infty\), and if \(x\to0^{-}\), \(\frac{1}{x^{2/3}}=\frac{1}{\sqrt[3]{x^{2}}}\to+\infty\). So \(\lim_{x\to0}\frac{1}{x^{2/3}}=\infty\).

65)

Step1: Recall tangent function

\(\tan x=\frac{\sin x}{\cos x}\). As \(x\to(\frac{\pi}{2})^{+}\), \(\cos x\to0^{-}\) and \(\sin x\to1\). So \(\lim_{x\to(\frac{\pi}{2})^{+}}\tan x=-\infty\).

66)

Step1: Recall secant function

\(\sec x=\frac{1}{\cos x}\). As \(x\to(-\frac{\pi}{2})^{-}\), \(\cos x\to0^{-}\). So \(\lim_{x\to(-\frac{\pi}{2})^{-}}\sec x=-\infty\).

67)

Step1: Recall cosecant function

\(\csc x=\frac{1}{\sin x}\). As \(x\to0^{+}\), \(\sin x\to0^{+}\), so \(\csc x\to+\infty\). Then \(\lim_{x\to0^{+}}(1 + \csc x)=\infty\).

68)

Step1: Recall cotangent function

\(\cot x=\frac{\cos x}{\sin x}\). As \(x\to0\), \(\lim_{x\to0}\cos x = 1\) and \(\lim_{x\to0}\sin x=0\). \(\lim_{x\to0}\cot x=\infty\), so \(\lim_{x\to0}(1-\cot x)=-\infty\).

Answer:

  1. \(-\infty\)
  2. \(\infty\)
  3. Does not exist
  4. \(\infty\)
  5. \(-\infty\)
  6. \(-\infty\)
  7. \(\infty\)
  8. \(-\infty\)