Solv Menu - HP 40gs User Manual

SOLV menu

DESOLVE
Computer Algebra System (CAS)
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
(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 y'(0) =c
0
Typing:
DESOLVE(d1d1Y(X)+Y(X) = COS(X),Y(X))
gives:
Y X ( ) ⋅
= cC0
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'
1
⋅
x + 2 cC1
x ( )
--------------------------
cos +
2
is written as d1Y(X)
⋅ x ( )
sin
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