Answer :
We need to find derivative of f(x) = cos (x – π/8)
Derivative of a function f(x) is given by –
f’(x) = {where h is a very small positive number}
∴ derivative of f(x) = cos (x – π/8) is given as –
f’(x) =
⇒ f’(x) =
We can’t evaluate the limits at this stage only as on putting value it will take 0/0 form. So, we need to do little modifications.
Use: cos A – cos B = – 2 sin ((A + B)/2) sin ((A – B)/2)
∴ f’(x) =
⇒ f’(x) =
Using algebra of limits –
⇒ f’(x) =
Use the formula –
∴ f’(x) =
Put the value of h to evaluate the limit –
∴ f’(x) = – sin (x – π/8 + 0) = – sin (x – π/8)
Hence,
Derivative of f(x) = cos (x – π/8) = – sin (x – π/8)
Rate this question :
How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
view all courses
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation

