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**palmstierna** a) I would start by as easy as possible say that the domain is what x can be, therefore x is ℕ. [-∞, ∞]. The codomain is what h can take based on anything on x. Therefore between -36/5 and 36/5.

b) The range is what the function can take from the domain. The cosine function has the range of [-1,1], so 0.2[−1,1]=[−0.2,0.2] so that [−0.2,0.2]−7=[−7.2,−6.8].

c) I'm lost on how to find out if it's an onto function though.. Since they wanted me to do a proof I was thinking of something that I read: "Each surjection f: X→Y leads to a partition of X in k parts. If we have a partition in k parts we have k! surjection that appears from the partition."