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Signed area…
Another very useful tool provided in the
menu is the
Signed Area…
tool. Before we begin to use it, make sure that
is switched on, and
that the cursor is on F1(X) - the quadratic. The
Signed Area…
tool is similar
to the Box Zoom in that it requires you to indicate the start and end points of
the area to be calculated.
Definite integrals
Suppose we want to find the definite integral:
3
2
2
5
4
x
x
dx
−
−
−
∫
Choose
and then
Signed Area…
You
will see the message shown right, asking you
to choose a starting point.
Press the
key, enter the value -2 and press
or
ENTER
. The
starting value will then be -2 so press
again (or
ENTER
) to accept it.
Another menu will appear, asking you to
indicate what area you wish to calculate. In
this case there are only two choices - between
F1(X) and the X axis, or between F1(X) and
F2(X).
If we had defined more functions in the
SYMB
view then this menu would be
longer. In this case we want the area between F1(X) and the x axis, so
position the highlight as shown and press
ENTER
.
The graphs will then reappear, with a message
requesting that you choose an end point. In the
screenshot shown right I have pressed
and entered the value 3 to move to that point
directly.