What does the 0,2pi mean?

Find the points of inflection of the graph of the function. [If an answer does not exist, enter DNE.} x} 2 9 sin x + 9 cos x, [[1, 271'] [|:| ) {smallerxvalue} (|:| ) {largerx-value} Describe the concavity. {Enter 1hurour answers using internal notation.) E E (X; r} (X; r} concave upward concave downward