(Construction Project 2: Circumscribed Circle of a Triangle) Step 1
Using a straightedge, draw an obtuse triangle. Label the vertices as A, B, and C.
Step 2
Draw the perpendicular bisector of side AC¯¯¯¯¯¯¯¯.
Place the compass point on A, then set the width of the compass so that the distance is slightly longer than half the length of AC¯¯¯¯¯¯¯¯. Then draw an arc that passes through AC¯¯¯¯¯¯¯¯ and has endpoints above and below point A.
Keep the compass setting and place the point of the compass at point C, then draw an arc that passes through AC¯¯¯¯¯¯¯¯ and has endpoints above and below point C. The intersection of these arcs constructs two points. Label these points D and E.
Using a straightedge, draw DE¯¯¯¯¯¯¯¯.
Step 3
Draw the perpendicular bisector of side BC¯¯¯¯¯¯¯¯.
Place the compass point on B, then set the width of the compass so that the distance is slightly longer than half the length of BC¯¯¯¯¯¯¯¯. Then draw an arc that passes through BC¯¯¯¯¯¯¯¯ and is above and below point B.
Keep the compass setting and place the point of the compass at point C, then draw an arc that passes through BC¯¯¯¯¯¯¯¯ and is above and below point B. The intersection of these arcs constructs two points. Label these points F and G.
Using a straightedge, draw FG¯¯¯¯¯¯¯¯.
Step 4
Mark the intersection of DE¯¯¯¯¯¯¯¯ and FG¯¯¯¯¯¯¯¯. Label this point H. Then place the point of the compass at point H, and set the width of the compass to one of the vertices of △ABC and draw a circle. If you did the construction correctly, this circle intersects each vertex of the triangle.

Step 5
Scan or take a photo of your final construction and save this file. You will upload this file in the next activity in this lesson.