If f(x)=sin−1(cosx)cos−1(sinx) ∀x∈[0,2π], then the number of point(s) of non differentiability is
If f(x) = [sin x] + [cos x], x∈[0,2π], where [.] denotes the greatest integer function. Then, the total number of points, where f(x) is non – differentiable, is