# Sage Calculus Tutorial -- continuity practice problems

Can anyone help me understand how to do some of the practice problems in the sage calculus tutorial? In particular, I'm stuck on problems 5 and on at the bottom of this page http://www.sagemath.org/calctut/conti...

For example, I am not sure how to define 'k'. As it stands, graphing the function in problem 5, sage does not know what to do with the variable 'k', because it is not defined.