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Add a tangent
Create a
derivative point
Geometry
8. We will now add a tangent to the curve, making point B
the point of tangency:
> More > Tangent
9. Tap on point B, press
A tangent is drawn
through point B.
(Depending on where
you placed point B, your
illustration might be
different from the one at
the right.)
We'll now make the
tangent stand out by giving it a bright color.
10. If the curve is selected, tap a blank area of the screen to
deselect, and then tap on the tangent to select it.
1 1. Press
Z
and select Change Color.
12. Pick a color from the color-picker, press
on a blank area of the screen. Your tangent should now
be colored.
13. Press
E
If there is only one point on the screen, pressing
automatically selects it. If there is more than one point, a
menu will appear asking you to choose a point.
14. With point B selected, use the cursor keys to move it
about.
Note that whatever you do, point B remains constrained
to the curve. Moreover, as you move point B, the tangent
moves as well. (If the moves off the screen, you can
always bring it back by dragging your finger across the
screen in the appropriate direction.)
15. Press
to deselect point B.
J
The derivative of a graph at any point is the slope of its
tangent at that point. We'll now create a new point that will
be constrained to point B and whose ordinate value is the
derivative of the graph at point B. We'll constrain it my forcing
its x coordinate (that is, its abscissa) to always match that of
E
and then press
to select point B.
J
.
J
and then tap
E
125
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