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Ex 12.2, 11 Find the derivative of the following functions: (ii) sec x Let f (x) = sec x f(x) = 1/cos⁑π‘₯ Let u = 1 & v = cos x So, f(x) = 𝑒/𝑣 ∴ f’(x) = (𝑒/𝑣)^β€² Using quotient rule f’(x) = (𝑒^β€² 𝑣 βˆ’ 𝑣^β€² 𝑒)/𝑣^2 Finding u’ & v’ u = 1 u’ = 0 & v = cos x v’ = – sin x Now, f’(x) = (𝑒^β€² 𝑣 βˆ’ 𝑣^β€² 𝑒)/𝑣^2 = (0(cos⁑〖π‘₯) βˆ’ (βˆ’sin⁑〖π‘₯) (1)γ€— γ€—)/(γ€–π‘π‘œπ‘ γ€—^2 π‘₯) (Derivative of constant is 0) (Derivative of cos x = – sin x) = (0 +γ€– sin〗⁑π‘₯)/(γ€–π‘π‘œπ‘ γ€—^2 π‘₯) = γ€– sin〗⁑π‘₯/(γ€–π‘π‘œπ‘ γ€—^2 π‘₯) = γ€– sin〗⁑π‘₯/cos⁑π‘₯ . 1/cos⁑π‘₯ = tan x . sec x Hence f’(x) = tan x . sec x Using tan ΞΈ = sinβ‘πœƒ/π‘π‘œπ‘ πœƒ & 1/cosβ‘πœƒ = sec ΞΈ

  1. Chapter 12 Class 11 Limits and Derivatives
  2. Serial order wise

About the Author

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo