# Ex 6.2,3 - Chapter 6 Class 12 Application of Derivatives

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Ex 6.2,3 Find the intervals in which the function f given by f ( ) = Sin is (a) strictly increasing in 0 , 2 f ( ) = sin f ( ) = cos Since cos > 0 for 0 , 2 So, f ( ) > 0 for 0 , 2 Thus, f is strictly increasing in 0 , 2 Ex 6.2,3 Find the intervals in which the function f given by f ( ) = Sin x is (b) strictly decreasing 2 , f ( ) = sin f ( ) = cos Since cos < 0 for 2 , So, f ( ) < 0 for 2 , Thus, f is strictly decreasing in 2 Ex 6.2,3 Find the intervals in which the function f given by f ( ) = Sin x is (c)neither increasing nor decreasing in (0 , ) Step 1: f ( ) = sin f ( ) = cos Step 2: Putting f ( ) = 0 cos x= 0 = 2 Step 3: Since (0 , ) we start number line from 0 to The point = 2 divides the interval (0 , ) into two disjoint interval i.e. 0 , 2 , 2 From 1st part , f ( ) is strictly increasing in 0 2 & from 2nd part, f( ) is strictly decreasing in 2 Hence f( ) is neither increasing nor decreasing in (0 , )

Chapter 6 Class 12 Application of Derivatives

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.