Functions Question 233

Question: $ \underset{x\to 0}{\mathop{\lim }}\frac{ln,(\cos x)}{x^{2}} $ is equal to

[AMU 2000]

Options:

A) 0

B) 1

C) $ \frac{1}{2} $

D) $ -\frac{1}{2} $

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Answer:

Correct Answer: D

Solution:

Applying L-Hospital?s rule, $ \underset{x\to 0}{\mathop{\lim }},\frac{\ln (\cos x)}{x^{2}} $ $ =\underset{x\to 0}{\mathop{\lim }},\frac{-\tan x}{2x} $ $ =\underset{x\to 0}{\mathop{\lim }},\frac{-{{\sec }^{2}}x}{2}=\frac{-1}{2} $ .