# Ex 13.2, 11

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Ex 13.2, 11 Find the derivative of the following functions: (i) sin x cos x Let f (x) = sin x cos x. Let u = sin x & v = cos x f(x) = uv So, f (x) = (uv) = u v + v u Here, u = sin x So, u = cos x & v = cos x So, v = sin x Now, f (x) = (uv) = u v + v u = cos x . cos x + ( sin x) sin x = cos2x sin2x = cos 2x Hence f (x) = cos 2x Ex13.2, 11 Find the derivative of the following functions: (ii) sec x Let f (x) = sec x f(x) = 1 cos Let u = 1 & v = cos x So, f(x) = f (x) = using quotient rule f (x)= 2 Finding u & v u = 1 u = 0 & v = cos x v = sin x Now, f (x) = = 2 = 0( cos ) ( sin ) (1) 2 = 0 + sin 2 = sin 2 = sin cos . 1 cos = tan x . sec x Hence f (x) = tan x . sec x Ex13.2, 11 Find the derivative of the following functions: (iii) 5 sec x + 4 cos x Let f (x) = 5 sec x + 4 cos x. Now, f (x) = ( 5 sec x + 4 cos x) = (5 sec x) + (4 cos x) = 5 (sec x . tan x) + 4 ( sin x) = 5 sec x . tan x 4 sin x Ex 13.2, 11 Find the derivative of the following functions: (iv) cosec x Let f (x) = cosec x f(x) = 1 sin Let u = 1 & v = sin x f(x) = So, f (x) = Using quotient rule f (x) = 2 Finding u & v u = 1 u = 0 & v = sin x v = cos x Now, f (x) = = 2 = 0 ( sin ) cos (1) 2 = 0 2 = 2 = sin . 1 sin = cot x cosec x = cosec x cot x Hence f (x) = cosec x cot x Ex13.2, 11 Find the derivative of the following functions: (v) f (x) = 3cot x + 5cosec x. Given f (x) = 3cot x + 5cosec x Now, f (x) = (3cot x + 5cosec x) = 3(cot x) + 5( cosec x) = 3cosec2x 5 cot x cosec x = 3 cosec2x 5 cosec x cot x Ex13.2, 11 Find the derivative of the following functions: (vi) f (x) = 5sin x 6 cos x + 7. Let f (x) = 5sin x 6cos x + 7 f (x) = (5 sin x 6 cos x + 7) = (5 sin x) (6 cos x) + (7) = 5 cos x 6 ( sin x ) + 0 = 5 cos x + 6 sin x Ex13.2, 11 Find the derivative of the following functions: (vii) f (x) = 2 tan x 7 sec x f (x) = 2 tan x 7 sec x. Now, f (x) = (2 tan x 7 sec x) = (2tan x) (7sec x) = 2 (tan x) 7 (sec x) = 2 sec2 x 7 (sec x tan x) = 2 sec2 x 7 sec x tan x

Chapter 13 Class 11 Limits and Derivatives

Example 2
Important

Example 3 Important

Ex 13.1, 6 Important

Ex 13.1,10 Important

Ex 13.1, 13 Important

Ex 13.1, 16 Important

Ex 13.1, 22 Important

Ex 13.1, 25 Important

Ex 13.1, 28 Important

Ex 13.1, 30 Important

Ex 13.1, 32 Important

Ex 13.2, 9 Important

Ex 13.2, 11 Important You are here

Example 20 Important

Example 21 Important

Example 22 Important

Misc 1 Important

Misc 6 Important

Misc 9 Important

Misc 24 Important

Misc 27 Important

Misc 28 Important

Misc 30 Important

Class 11

Important Question for exams Class 11

- Chapter 1 Class 11 Sets
- Chapter 2 Class 11 Relations and Functions
- Chapter 3 Class 11 Trigonometric Functions
- Chapter 4 Class 11 Mathematical Induction
- Chapter 5 Class 11 Complex Numbers
- Chapter 6 Class 11 Linear Inequalities
- Chapter 7 Class 11 Permutations and Combinations
- Chapter 8 Class 11 Binomial Theorem
- Chapter 9 Class 11 Sequences and Series
- Chapter 10 Class 11 Straight Lines
- Chapter 11 Class 11 Conic Sections
- Chapter 12 Class 11 Introduction to Three Dimensional Geometry
- Chapter 13 Class 11 Limits and Derivatives
- Chapter 14 Class 11 Mathematical Reasoning
- Chapter 15 Class 11 Statistics
- Chapter 16 Class 11 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.