The Square Root of Minus One

Subtract from the size of your room the size of your cupboard. Minus one cupboard. The sides of the cupboard measure: The square root of minus one. The measurement of the sides may be described either as one unit of cupboard length or as minus one unit of floor wall. This is supposed to be an "imaginary" number because we supposedly can't draw a practical diagram of it or find a practical example. But we can. So la! Soundtrack made in VSThost.