hp40g+.book Page 68 Friday, December 9, 2005 1:03 AM

 

gives:

 

 

 

 

5

1

⋅ π

2

 

– -- +

--

 

 

4

6

 

 

Psi

Returns the value of the Digamma function at a.

 

The Digamma function is defined as the derivative of

 

ln(Γ(x)), so we have PSI(a,0) = Psi(a).

 

Example

 

 

 

Typing:

 

 

 

 

Psi(3)

 

 

 

 

and pressing

 

gives:

 

 

 

 

.922784335098

REORDER

Reorders the input expression following the order of

 

variables given in the second argument.

 

Example

 

 

 

Typing:

 

 

 

 

REORDER(X2 + 2 · X · A + A2 + Z2 – X · Z, A AND X

 

AND Z)

 

 

gives:

 

 

 

 

A2 + 2 ⋅ X ⋅ A + X2 – Z ⋅ X + Z2

SEVAL

SEVAL simplifies the given expression, operating on all

 

but the top-level operator of the expression.

 

Example

 

 

 

Typing:

 

 

 

 

SEVAL(SIN(3 · X -– X) + SIN(X + X))

 

gives:

 

 

 

 

sin(2 ⋅ x) + sin(2 ⋅ x)

SIGMA

Returns the discrete antiderivative of the input function,

 

that is, the function G, that satisfies the relation G(x + 1)

 

– G(x) = f(x). It has two arguments: the first is a function

 

f(x) of a variable x given as the second argument.

14-68

 

 

Computer Algebra System (CAS)