HP 40gs User Manual page 216

ISOLATE
14-34
To produce the solutions for y(0) = 1, type:
SUBST Y X ( ) (
cC0 COS X ( ) ⋅
which gives:
⋅
2 cos
y x ( )
--------------------------------------------------------------------------------- -
=
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 +
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:
4
ISOLATE(X -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)
=
⋅
X + 2 cC1
⋅ SIN X ( ) cC0
+ - - - - - - - - - - - - - - - -
2
x ( ) ( ⋅ )
+ x + 2 cC1
2
2 + x
⋅ x ( )
----------- -
sin
2
Computer Algebra System (CAS)
1 )
, =
⋅ x ( )
sin