Sketch the graph of f (t) = sin t + cos t for -2 t

Sketch the graph of f (t) = sin t + cos t for -2π ≤ t ≤ 2p, using the following steps:

(a) Find all t between -2π and 2π such that f′(t) = 0. Plot the corresponding points on the graph of y = f (t).

(b) Check the concavity of f (t) at the points in part (a). Make sketches of the graph near these points.

(c) Determine any inflection points and plot them. Then, complete the sketch of the graph.