Question

Find the intervals in which the function f given by
f(x)=sinx + cosx ,o_x_2pi is strictly increasing or strictly decreasing

Answer 1

The function f(x) = sinx + cosx is strictly increasing on the interval [0, π/4) ∪ (5π/4, 2π] and is strictly decreasing on the interval (π/4, 5π/4).