# Quadric surfaces?

qqchico
why are they called quadric surfaces?

## Answers and Replies

CinderBlockFist
well the definition in my book gives:

Q quadric surface is the graph of a second-degree equation in three variables x, y, and z. So i guess cause its the graph of a quadratic equation in 3-D.

qqchico
I have that too but i don't think the teacher would give such an easy question. thanks a bunch.

Science Advisor
Homework Helper
Why are "quadratic equation" called "quadratic" when "quad" means 4?

Apparently because a square has 4 sides!

Extends, then to "quadric" surfaces, surfaces whose equations involve 2 nd power.