Online Geometry: Angles Theorems and Problems- Table of Content, Page 1

Euclid's Elements Book I, 23 Definitions. One-page visual illustration. Angles and more.
Euclid's Elements Book. Index.

Points, Theorems and Problems - Index.
Vertex.

Acute Angle in the Real World - Slideshow.

Meanings and syntactic of 'ANGLE'.
Created using Wordflex Touch Dictionary for iPad in association with Oxford University Press.

Obtuse Angle. Theorems and Problems.

Angles: 30, 60, 120 degrees.

Angles: 45, 135 degrees.

Angle Bisector.

Isogonal Lines.
Theorems and Problems.

Billiards and Geometry - Index
Angles of Incidence and Reflection.

Book I, Proposition 9: Bisect a given angle

Incenter. Index.
Angle bisectors.

Excenter. Index.
Interior and Exterior Angle bisectors.

PRK and Laser Eye Surgery.
The light rays, upon being transmitted through the lens, are refracted to an angle causing them to converge directly at the fovea, which is the area of the retina with the highest concentration of light sensitive cells.

Inca Stone of Twelve Angles, Cuzco. Tunnel effect.

Euclid's Elements Book VI, Proposition 3: Angle Bisector Theorem

Animated illustration of the celebrated Morley's angle trisector theorem 

Morley's Triangle & Center: Trisection of angles.

Blanchet Theorem. Altitude, Angle Bisector.

Isogonic-Jacobi Theorem: Using TracenPoche Dynamic Geometry Software

Mascheroni Construction with compass alone. Midpoint of a segment. Equal angles.

Interactive Simson Line. Dynamic Geometry.
Step-by-Step construction, Manipulation, and animation.
Vertical angles.

Triangle: Incircle, Perpendicular, Angle Bisector. Dynamic Geometry.
Step-by-Step construction, Manipulation, and animation.

Geometry Problem 873
Quadrilateral, Diagonal, Triangle, Angle Bisector, Congruence.

Geometry Problem 872
Quadrilateral, Triangle, Angle, 30, 90 degrees.

Geometry Problem 867
Isosceles Triangle, Median, Perpendicular, Angle, Congruence.

Geometry Problem 875
Congruent Circles, Intersecting Circles, Secant, Center, Angle Trisection, Triple Angle.

Geometry Problem 859
Isosceles Right Triangle, Angles,18, 45 Degrees, Congruence, Perpendicular bisector.

Geometry Problem 858
Isosceles Right Triangle, Cevian, Ratio 2:1, 45 Degrees, Congruence, Angles, Auxiliary Lines.

Geometry Problem 857
Triangle, Median, Midpoint, Angles, 30, 45 Degrees, Congruence, Auxiliary Lines.

Geometry Problem 856
Quadrilateral, Diagonals, Triangle, Angles, 30 degrees, Congruence, Auxiliary lines.

Geometry Problem 855
Quadrilateral, Triangle, Angles, 30 degrees, Congruence, Auxiliary lines.

Geometry Problem 851
Triangle, Triple side, Angles, 90 Degrees, Special Right triangle, Sides ratio 1:3.

Geometry Problem 850
Triangle, Double side, Angles, 90 Degrees. Special Right triangle.

Geometry Problem 849
Special Right triangle, Catheti or legs ratio 1:3, 18.5 Degrees. Double angle.

Geometry Problem 835
Isosceles Triangle, Double Angle, Triple Angle, Auxiliary Lines.

Geometry Problem 832
Quadrilateral, Isosceles triangle, 70-70-40 degrees, Congruence, Auxiliary lines, Equilateral triangle.

Geometry Problem 831
Quadrilateral, Diagonal, Midpoint, Opposite Angles, Congruence, Parallelogram.

Geometry Problem 830
Quadrilateral, Triangle, Angles, 30 degrees, Congruence.

Geometry Problem 820.
Triangle, Cevian, Angles, 30 Degrees.

Geometry Problem 819.
Quadrilateral, Triangle, Angles, 30 degrees.

Geometry Problem 818.
Square, Triangle, Angle.

Geometry Problem 814.
Two Equilateral Triangles with a common Vertex, Angle.

Geometry Problem 796
Triangle, Altitude, Measurement of Angles.

Geometry Problem 776
Triangle, Isogonal lines, Congruent angles, Perpendicular, Concyclic points, Circle, Center, Midpoint.