HP 40gs hp 40gs_user's guide_English_E_HDPMSG40E07A.pdf - Page 216
Example 2
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hp40g+.book Page 34 Friday, December 9, 2005 1:03 AM ISOLATE 14-34 To produce the solutions for y(0) = 1, type: SUBST(Y(X) = cC0 ⋅ COS(X) + -X--+---2---⋅--c--C---1 ⋅ SIN(X), cC0 = 1 ) 2 which gives: y(x) = 2-----⋅---c---o---s---(--x x----+-----2-----⋅---c---C----1 s--i--n---(---x---) 2 Example 2 Solve: y" + y = cos(x) y(0) = 1 y'(0) = 1 It is possible to solve for the constants from the outset. Typing: DESOLVE((d1d1Y(X)+Y(X)=COS(X)) AND (Y(0)=1) AND (d1Y(0)=1),Y(X)) gives: Y(x) = cos x + 2-----+-----x2 ⋅ sin (x ) The zeros of an expression ISOLATE returns the values that are the zeros of an expression or an equation. ISOLATE has two parameters: an expression or equation, and the name of the variable to isolate (ignoring REALASSUME). Typing: ISOLATE(X4-1=3,X) gives in real mode: (x = √2) OR (x = −√2) and in complex mode: (x = √2 · i) OR (x = −√2) OR (x = −(√2 · i)) OR (x = √2) Computer Algebra System (CAS)