Ex 6.2, 12 Which of the following functions are strictly decreasing on (0 ,𝜋/2)? (A) cos 𝑥f(𝑥) = cos 𝑥 f’(𝒙) = – sin 𝒙 Since, sin 𝑥 > 0 for 𝑥 ∈ (0 , 𝜋/2) So, –sin 𝒙 < 0 for 𝑥 ∈ (0 , 𝜋/2) ∴ f’(𝑥) < 0 for 𝑥 ∈ (0 , 𝜋/2) So, f is strictly decreasing in (0 , 𝜋/2)

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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