Question

If f(x) = |cos x – sinx|, find `"f'"(pi/6)`

Answer 1

When 0 < x < `pi/4`,cos x > si x

So that cos x – sin x > 0

i.e. f(x) = cos x – sin x 

⇒ f′(x) = – sin x – cos x

Hence `"f'"(pi/6) = - sin  pi/6 - cos  pi/6`

=` 1/2 (1 + sqrt(3))`.