Calculus songs

So, here's a thing I do sometimes: students suggest song parodies based on calculus concepts. I take the best idea, write the lyrics, and sing it into a laptop microphone over a karaoke track. Here are the results.

On differentiability: "Differentiable" (Lyrics)
On l'Hôpital's rule: "Some Limit of a Ratio" (Lyrics)
On the antiderivative of 1/(4+9x²): "I'll Make arctan out of u" (Lyrics)
On the radius of convergence of a power series: "Party in the US(x – a)" (Lyrics)