Texas Instruments TITANIUM TI-89 - Manual (Page 808)

808 Appendix A: Functions and Instructions
DelType
DelType var_type
Deletes all unlocked variables of the type
specified by
var_type .
Note: Possible values for var_type are:
ASM, DATA, EXPR, FUNC, GDB, LIST, MAT, PIC,
PRGM, STR, TEXT, AppVar_type_name, All.
Deltype “LIST” ¸ Done
DelVar CATALOG
DelVar var1 [, var2 ] [, var3 ] ...
Deletes the specified variables from memory.
2! a ¸ 2
(a+2)^2 ¸ 16
DelVar a ¸ Done
(a+2)^2 ¸ (a + 2)ñ
deSolve()
MATH/Calculus menu
deSolve( 1stOr2ndOrderOde , independentVar ,
dependentVar ) ⇒ ⇒ ⇒ ⇒ a general solution
Returns an equation that explicitly or implicitly
specifies a general solution to the 1st- or 2nd-
order ordinary differential equation (ODE). In the
ODE:
• Use a prime symbol ( ' , press 2 È ) to
denote the 1st derivative of the dependent
variable with respect to the independent
variable.
• Use two prime symbols to denote the
corresponding second derivative.
The ' symbol is used for derivatives within
deSolve() only. In other cases, use d ( ) .
The general solution of a 1st-order equation
contains an arbitrary constant of the form
@k ,
where k is an integer suffix from 1 through 255.
The suffix resets to 1 when you use ClrHome or
ƒ 8: Clear Home . The solution of a 2nd-order
equation contains two such constants.
Note: To type a prime symbol ( ' ), press
2 È.
deSolve(y''+2y'+y=x^2,x,y)¸
y=(
@ 1шx+ @ 2)ш e ë x +xñì4øx+6
right(ans(1))!temp ¸
( @ 1шx+ @ 2)ш e ë x +xñì4øx+6
d (temp,x,2)+2ù d (temp,x)+tempìx^2
¸ 0
DelVar temp ¸ Done
Apply solve() to an implicit solution if you want
to try to convert it to one or more equivalent
explicit solutions.
deSolve(y'=(cos(y))^2ùx,x,y) ¸
tan(y)=
xñ
2
+@3
When comparing your results with textbook or
manual solutions, be aware that different
methods introduce arbitrary constants at different
points in the calculation, which may produce
different general solutions. solve(ans(1),y) ¸
y=tanê
( 2 2 @ 3
2
x + i
)
+@n1øp
ans(1)|@3=cì1 and @n1=0 ¸
y=tanê
( xxxxс +2 +2 +2 +2ш((((ccccì 1111))))
2222
)
deSolve( 1stOrderOde and initialCondition ,
independentVar , dependentVar )
⇒ ⇒ ⇒ ⇒ a particular solution
Returns a particular solution that satisfies
1stOrderOde and initialCondition . This is usually
easier than determining a general solution,
substituting initial values, solving for the arbitrary
constant, and then substituting that value into
sin(y)=(yù e ^(x)+cos(y))y'!ode ¸
sin(y)=( e x ø y+cos(y))øy'
deSolve(ode and y(0)=0,x,y)!soln
¸
ë (2øsin(y)+yс)
2
====л(((( e xxxx м 1) 1) 1) 1)ш e ë xxxx ø sin(y) sin(y) sin(y) sin(y)