HP 40gs User Manual
Page 250
14-68
Computer Algebra System (CAS)
gives:
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(X
2
+ 2 · X · A + A
2
+ Z
2
– X · Z, A AND X
AND Z)
gives:
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:
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.
5
4
---
–
1
6
---
π
2
⋅
+
A
2
2
+
X A
⋅ ⋅
X
2
Z
–
+
X Z
2
+
⋅
2 x
⋅
(
)
sin
2 x
⋅
(
)
sin
+
hp40g+.book Page 68 Friday, December 9, 2005 1:03 AM