If f(x)=sin(x)+cos(x)f(x) = \sin(x) + \cos(x)f(x)=sin(x)+cos(x), find the time t∈[0,π]t \in [0, \pi]t∈[0,π] where velocity is zero.
π/4\pi/4π/4
π/2\pi/2π/2
3π/43\pi/43π/4
π\piπ