HP Prime Graphing Calculator - Manual (Page 163)

Geometry 159
Special
Circumcircle A circumcircle is the circle
that passes through each of
the triangle’s three vertices,
thus enclosing the triangle.
Tap at each vertex of the
triangle, pressing
E
after each tap.
Incircle An incircle is a circle that is
tangent to each of a
polygon’s sides. The HP
Prime can draw an incircle
that is tangent to the sides of
a triangle.
Tap at each vertex of the
triangle, pressing
E
after each tap.
Excircle An excircle is a circle that is tangent to one segment of a
triangle and also tangent to the rays through the segment’s
endpoints from the vertex of the triangle opposite the segment.
Tap at each vertex of the
triangle, pressing
E
after each tap.
The excircle is drawn tangent
to the side defined by the last
two vertices tapped. In the
example at the right, the last
two vertices tapped were A
and C (or C and A). Thus the excircle is drawn tangent to the
segment AC.