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Piecewise defined functions
It is possible to graph piecewise defined functions using the Function aplet,
although it involves literally splitting the function into pieces.
For example:
2
3
;
2
( )
2
;
2
1
3
;
1
x
x
f x
x
x
x
x
+
< −
=
−
− ≤ ≤
−
≥
To graph this we need to enter it into the
SYMB
view as
three separate functions:
F1(X)=(X+3)/(X < -2)
F2(X)=(X
2
-2)/(X
≥
-2 AND X
≤
1)
F3(X)=(3-X)/(X
≥
1)
Note:
AND can be found on the (-) key
.
The reason why this works is that the (X < -2)
and the (X
≥
-2 AND X
≤
1) expressions are
evaluated as being either true (which for
computers has a value of 1) or false (which
has a value of 0).
By dividing by the domain expression we are effectively dividing by 1 inside
the range (no effect) or dividing by zero outside the domain, making the
function undefined. Since undefined values are not graphed, this produces
the desired effect.