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 one of the few mathematical tools that can be used. to provide solution to a wide variety of large, complex managerial problems. For example, an oil refinery can vary its product-mix by its choice among the different. grades of crude oil available from various parts of the world.