HP 40gs - Manual (Page 215)

Computer Algebra System (CAS) 14-33
Typing:
XQ(1.414213562)
gives:
√2
SOLV menu
The SOLV menu contains functions that enable you to
solve equations, linear systems, and differential
equations.
DESOLVE 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 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)=c
0
y’(0) =c
1
Typing:
DESOLVE(d1d1Y(X)+Y(X) = COS(X),Y(X))
gives:
cC0 and cC1 are integration constants (y(0) = cC0 y’(0)
= cC1).
You can then assign values to the constants using the
SUBST command.
y'
Y X ( ) cC0 x ( ) cos ⋅
x 2 cC1 ⋅ +
2
-------------------------- x ( ) sin ⋅ + =
hp40g+.book Page 33 Friday, December 9, 2005 1:03 AM