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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
54
xdx
−
−−
∫
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.
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