Triangles: Theorems and Problems 20

Proposed Problem 328.
Triangle, Incircle, Tangency Points, Parallel, Midpoint.

Proposed Problem 326.
Equilateral triangle, Semicircle, Equal arcs.

Proposed Problem 322.
Square, Inscribed circle, Tangent, Triangle area.

Proposed Problem 321.
Triangle, Incenter, Excircle, Midpoint of the Altitude, Collinearity.

Proposed Problem 320.
Triangle, Circumcircle, Incenter, Excenter, Collinear points.

Proposed Problem 319.
Triangle, Altitudes, Perpendiculars, Collinear points.

Proposed Problem 318.
A Scalene triangle, Altitudes, Collinear points.

Proposed Problem 317.
Right triangle and Inscribed Squares.

Proposed Problem 292.
Triangle, Parallel, Congruence, Similarity.

Proposed Problem 291.
Triangle, Circle, Circumradius, Perpendicular.

Euclid's Elements, Book X, Lemma for Proposition 33
One page visual illustration.

Proposed Problem 287: Regular Octagon. Triangles

Proposed Problem 286: Square, Midpoints, Octagon.
Triangles

Proposed Problem 282.
Right Triangle, Cevian, Angles, Perpendicular, Congruence.

Proposed Problem 281.
Triangles, Angles, Isosceles, Equilateral.

Proposed Problem 279.
Tangent Circles, Common External Tangent, Chords, Inradius, Triangle.

Proposed Problem 276.
Square, 90 degree Arcs, Circle, Radius, Triangle.

Proposed Problem 274.
Isosceles Triangle, 80-80-20, Angles.

Proposed Problem 273.
Triangle, Perpendiculars, Area of Squares.

Proposed Problem 270.
Tangent Circles, Common external tangent, Fractional exponents.

Proposed Problem 269.
Right Triangle, Altitude, Perpendicular, Projection.

Proposed Problem 268.
Right Triangle, Catheti and Altitude.

Proposed Problem 267.
Right Triangle, Product of Catheti.

Proposed Problem 266.
Right Triangle, Altitude, Geometric Mean.

Proposed Problem 265.
Right Triangle, Pythagorean Theorem.

Proposed Problem 264.
Right Triangle, Altitude, Leg projection, Hypotenuse, Similarity, Geometric mean.

Proposed Problem 263.
Triangle, Median, Altitude, Orthogonal Projection, Sides.