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Application of Derivatives

NCERT Exemplar Class 12

CBSE

Grade 12

Question:

The function $f(x) = \cos x$ is strictly decreasing on:
(a) $(0, \pi)$
(b) $(\pi, 2\pi)$
(c) $(0, 2\pi)$
(d) $(-\pi/2, \pi/2)$

Step-by-Step Solution

f'(x) = -sin x < 0 for x in (0, \pi). [1.0 Mark]

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🎯 Official CBSE Marking Scheme:
Selecting $(0, \pi)$: 1.0 Mark

Correct Answer: $(0, \pi)$

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