Triangles: Theorems and Problems 38

Steiner Point
Triangle center. 

Proposed Problem 26
Right Triangle, altitude, incircles and inradius.

Proposed Problem 25
Right Triangle, altitude, incircles and inradius.

Proposed Problem 24
Right Triangle, altitude, incircles and inradii.

Proposed Problem 23
Right Triangle, altitude, incircles and inradii.

Proposed Problem 22
Right Triangle, altitudes, incircles and inradii.

Proposed problem 21
Acute triangle, orthocenter, diameter, tangents.

Symmedian (Lemoine) Point
Triangle Center

Heron's Formula. Triangle.
Key facts and a purely geometric step-by-step proof.
 

Triangle and Squares. theorems. Visual illustrations.

Problem 11.
Right triangle, cevian, angles, degrees.

Problem 12.
Triangle, cevian, equal segments, angles, degrees.

Problem 13.
Triangle, cevian, congruence, angles, degrees.

Problem 14.
Triangle, median, angles, degrees.

Problem 15.
Triangle, cevian, sum of segments, angles, angle bisector, 30 degrees.

Problem 16.
Triangle, cevian, perpendicular, angles, angle bisector, degrees.

Problem 17.
Right triangle, altitude, and angles.

Problem 18.
Right triangle, cevian, and angles.

Problem 19.
Isosceles Right triangle, perpendicular, Excenter, Congruence.

Problem 20.
Right triangle, altitude, incircles and inradii.