This shape was brilliant / This shape was pure.
I saw three angles / Of that I'm sure.
And I saw three pointy corners / And then I saw three straight sides.
The top was very narrow / And the base was oh so wide
(Telly says, "Wait that sounds like…")
A Triangle / My triangle
Oh triangle, it's true.
I saw your shape / In a crowded place
Now I don't know what to do.

Eventually they even manage to force a rhyme with "hypotenuse."

I'm not a fan of the original song, but this actually makes me respect James Blunt a bit, just for having a sense of humor. And, to paraphrase Telly, there's nothing like a Euclidean love story.