Sum of squares Puns

I said, 'Sure.'

She sighed.

'I saw you and your ex studying Pythagoras' theorem in the library.'

'Oh, you did?' I asked.

She paused. 'So, how do you explain that?'

'Easily,' I replied. 'It's when the square on the hypotenuse of a right-angled triangle is equal to the sum of the squares on the other two sides.'

I was in a stats course and we were doing some regression. To estimate the parameters, we need to square a bunch of differences and add them up. This is called the "Sum of Squares," so I leaned over to my friend and asked "Why not all of them?"

Fortunately my friends are needs, too.