Altitudes and orthocenter
Hee Jung Kim
1. Construct any acute triangle ABC and its circumcenter and circumcircle (the circumscribed circle) of the triangle.
2. Construct the three altitude AD, BE, and CF. Extend each altitude to its intersection with the circumcircle at corresponding points P, Q, and R.
3. Find . See GSP.
4. Prove . To see the proof, click here.