Visualizing a family of curves can give an intuitive feeling for their properties, but sometimes that intuition is wrong. So it is helpful to be able to compute, check, and display results.
Each curve has a vertical tangent at

, which comes from taking the limit. So there is no derivative at

.
At

, the curves with

odd never have the same tangent and are never horizontal.
At

, the curves with

even alternate between having a derivative of

and

.
At

, the curves with

odd always have the same tangent. At (

, 0), the curves with

even always have the same tangent (different from the

odd case).