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

Using CAS functions in HOME

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 when 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:

FACTOR(XQ(45)) = 32 × 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:

DERVX(S12 + 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:

S12 – 4 × S2 E1

then you get:

DERVX(E1) = S1 × 2

DERIV(E1, S2) = –4

INTVX(E1) = 1/3 S13 – 4 × (S2 × S1)

Computer Algebra System (CAS)

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