NAME: __________________________________
DATE: _______________ BLOCK: ___________
Lab: Explore the Circumcenter
 Construct Triangle ABC. (You might want to change colors of segments as
you progress through the lab so it is easier to differentiate segments. Select
the segments you would like to change the color of, go to Display->Color)
 Select all three sides of the triangle and construct the midpoint of each side.
 Label the midpoints D, E and F.
 Select Midpoint D and the side it lies on, construct a perpendicular line.
Repeat that process for the other midpoints.
o What type of line did your create? (Recall: The created line
intercepted the Midpoint and was Perpendicular to the side…)
 Select the point of intersection of the perpendicular bisectors with your
arrow tool and then label the point as G.
NAME: __________________________________
DATE: _______________ BLOCK: ___________
INVESTIGATE: Using your Arrow from the Toolbox, select and grab
point A and alter the way your triangle looks.
o Move point A around so Triangle ABC is acute. (If you forgot what
an “Acute Triangle” is Google it/ask a friend!) Move Point A
around, as long as your triangle is acute where does Point G lie?
o Move point A around so Triangle ABC is obtuse. Move Point A
around, as long as your triangle is obtuse where does Point G lie?
o Move point A around again so Triangle ABC is a Right Triangle.
Where is point G now? Why does it make sense to be there?
CONNECT THE IDEAS: Fill in the Blanks:
The Point of Intersection of the Perpendicular Bisectors of an Acute
Triangle will always lay _______________________ the triangle.
The Point of Intersection of the Perpendicular Bisectors of an Obtuse
Triangle will always lay _______________________ the triangle.
The Point of Intersection of the Perpendicular Bisectors of a Right Triangle
will always lay _______________________ the triangle on the
_________________________.
NAME: __________________________________
DATE: _______________ BLOCK: ___________
 Construct Segments AG, BG, and CG. (You may want them to look
different from the other segments/lines, I selected mine and made them
dashed and a different color)
INVESTIGATE: Find the measures of all three segments you just created.
(Select the Segment and Measure -> Length)
o What do you notice?
o Grab point A again and move it around so your triangle changes,
(obtuse, acute, right) what do you notice about segments AG, BG
and CG?
NAME: __________________________________
DATE: _______________ BLOCK: ___________
CONNECT THE IDEAS: Fill in the Blank:
 The Point of Intersection of the Perpendicular Bisectors of an triangle will
always be _______________________ to the vertices of the triangle.
EXPAND!
 Select point G and segment BG. Construct a Circle by Center and Radius.
o What does the circle do to the Triangle?
o Manipulate your triangle by moving point A. What do you notice
about the circle?
o How do segments AG, BG, and CG relate to the circle?
GET CREDIT! Drag a Textbox using the Letter in the Toolbox. Write Your
Name along with “Circumcenter” and your block number. Print it out and hand in
your packet with your sketch for full credit.