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LINEAR?(expression,var.name)
This is another of those functions which is probably aimed more at the
programmer than at the normal user. It is designed to test whether a
supplied expression is linear or non-linear in the variable you specify,
returning zero for non-linear and 1 for linear.
Eg. Suppose we use the expression
2
4
AX
B
− +
If X is the variable and A and B are both
constants (say
A=4, B=5
) then the
expression
2
4
AX
B
− +
would become
2
4
5 4
X
− +
which would be non-linear. Thus
LINEAR?
returns zero (right).
On the other hand, if X were one of the
constants (say
X=
6) and A were the variable,
then the expression
2
4
AX
B
− +
would
become
2
6
5 4
A
× − +
or
36
1
A
−
, which is
linear. Thus
LINEAR?
would return 1.
The main use for this is going to be when a programmer does not know in
advance what function the user is going to type in.
QUAD(expression,var.name)
This function uses the quadratic formula
2
4
2
b
b
ac
x
a
− ±
−
=
to give both roots of a
quadratic, using the ‘
S1
’ formal variable to
represent the
±
symbol. The quadratic is
entered as an expression, and you must indicate which variable is being
solved for, since you could have an equation such as
2
5
0
Px
Qx
+
− =
where
P
and
Q
were memory values, and you would need to specify to solve for
X
.
