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.

1. 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 endpointsabove and below point A.
2. Keep the compass setting and place the point of the compass at point C, then draw an arc that passes through ACand has endpointsabove and below point C. The intersection of these arcs constructs two points. Label these points D and E.
3. Using a straightedge, draw DE.

Step 3

Draw the perpendicular bisector of side BC.

1. 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 BCand is above and below point B.
2. Keep the compass setting and place the point of the compass at point C, then draw an arc that passes through BCand is above and below point B. The intersection of these arcs constructs two points. Label these points F and G.
3. Using a straightedge, draw FG.

Step 4

Mark the intersection of DEand 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.

Instructions for Using the Interactive Tool