Learning Guide Learning Guide

48 • Chapter 3: Finding SolutionsYou can also choose to solve for a subset of the unknowns. Then Maplereturns the solutions in terms of the other unknowns.> s2 := solve({eqn1,eqn2,eqn3}, { x, y, z});s2 := {x = − 52713 − 7 t − 28 u, z = −7013 13 − 7 t − 5913 u,y = 63513+ 12 t +7013 u}Exploring SolutionsYou can explore the parametric solutions found at the end of the previoussection. For example, evaluate the solution at u = 1 and t = 1.> eval( s2, {u=1,t=1} );{x = −64613 , z = −22013 , y = 86113 }Suppose that you require the solutions from solve in a particularorder. Since you cannot fix the order of elements in a set, solve will notnecessarily return your solutions in the order x, y, z. However, lists dopreserve order. Try the following.> eval( [x,y,z], s2 );[− 52713 − 7 t − 28 635 70u, + 12 t + u, −7013 13 13 13 − 7 t − 5913 u]This command not only fixed the order, but it also extracted theright-hand side of the equations. Because the order is fixed, you knowthe solution for each variable. This capability is particularly useful if youwant to plot the solution surface.> plot3d(%, u=0..2, t=0..2, axes=BOXED);