Find the range of f(x)=cos(x)f(x) = \cos(x)f(x)=cos(x) on [0,π][0, \pi][0,π].
[−1,0)∪{1}[-1, 0) \cup \{1\}[−1,0)∪{1}
[0,1][0, 1][0,1]
[−1,1][-1, 1][−1,1]
[−1,0][-1, 0][−1,0]