Using Cas Functions In Home - HP 40gs User Manual

hp40g+.book Page 7 Friday, December 9, 2005 1:03 AM

Using CAS functions in HOME

Computer Algebra System (CAS)
You can use many computer algebra functions directly in
the HOME screen, as long as you take certain
precautions. CAS functions that take matrices as an
argument work only from HOME.
CAS functions can be accessed by pressing
MATH menu is displayed. You can also directly type a
function name when you are in alpha mode.
Note that certain calculations will be performed in
approximate mode because numbers are interpreted as
reals instead of integers in HOME. To do exact
calculations, you should use the XQ command. This
command converts an approximate argument into an
exact argument.
For example, if Radians is your angle setting, then:
ARG(XQ(1 + i)) = π/4 but
ARG(1 + i) = 0.7853...
Similarly:
2
FACTOR(XQ(45)) = 3 × 5 but
FACTOR(45) = 45
Note too that the symbolic HOME variable S1 serves as
the current variable for CAS functions in HOME. For
example:
2
DERVX(S1 + 2 × S1) = 2 × S1 + 2
The result 2 × S1 + 2 does not depend on the Equation
Writer variable, VX.
Some CAS functions cannot work in HOME because they
require a change to the current variable.
Remember that you must use S1,S2,...S5, s1,s2,...s5,
and n1,n2,...n5 for symbolic variables and E0, E1,...E9
to store symbolic expressions. For example, if you type:
2
S1 – 4 × S2 E1
then you get:
DERVX(E1) = S1 × 2
DERIV(E1, S2) = –4
3
INTVX(E1) = 1/3 S1 – 4 × (S2 × S1)
when
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