HP 40gs hp 40gs_user's guide_English_E_HDPMSG40E07A.pdf - Page 215

hp40g+.book Page 33 Friday, December 9, 2005 1:03 AM SOLV menu DESOLVE Typing: XQ(1.414213562) gives: √2 The SOLV menu contains functions that enable you to solve equations, linear systems, and differential equations. Solve differential equations DESOLVE enables you to solve differential equations. (For linear differential equations having constant coefficients, it is better to use LDEC.) DESOLVE has two arguments: 1. the differential equation where y' is written as d1Y(X) (or the differential equation and the initial conditions separated by AND), 2. the unknown Y(X). The mode must be set to real. Example 1 Solve: y" + y = cos(x) y(0)=c0 y'(0) =c1 Typing: DESOLVE(d1d1Y(X)+Y(X) = COS(X),Y(X)) gives: Y(X) = cC0 ⋅ cos(x) + x-----+-----2----⋅---c---C----1-- ⋅ sin(x) 2 cC0 and cC1 are integration constants (y(0) = cC0 y'(0) = cC1). You can then assign values to the constants using the SUBST command. Computer Algebra System (CAS) 14-33