sand dollar. n. 1. Any of various thin circular echinoderms of the order Clypeasteroida, especially Echinarachnius parma, of coastal northern Atlantic and Pacific waters, having a covering of short movable spines.
One reason why linear algebra is very useful is that linear transforms of normal variables are normal. If x ~ N(a, A), then Bx+b ~ N(Ba+b, BABT). In a way, when everything is linear and normal, everything is nice and analytically tractable.
Linear programming is an extremely general technique, and its applications are limited mainly by our imaginations and our ingenuity. The objective function indicates how much each variable contributes to the value to be optimized in the problem. The objective function takes the following general form: