Triangles: Theorems and Problems 6

Geometry Problem 1275.
Equilateral Triangle, Perpendicular, Projection, Metric Relations, Measurement.

Geometry Problem 1274.
Isosceles Triangle, 80-20-80 Degrees, Area, Inradius, Circumradius, Angle Bisector, Metric Relations, Measurement.

Geometry Problem 1273.
Circle, Tangent, Secant, Midpoint, Isogonal Lines, Congruent Angles.

Geometry Problem 1272.
Isosceles Triangle, Median, Midpoint, Perpendicular, 90 Degrees, Angles, Congruence.

Geometry Problem 1271.
Triangle, Incircle, Incenter, Excircle, Excenter, Escribed Circle, Tangency Points, Six Concyclic Points.

Geometry Problem 1270.
Triangle, Excircle, Excenter, Escribed Circle, Tangency Points, Perpendicular, 90 Degrees, Angle Bisector.

Geometry Problem 1269.
Triangle, Incircle, Incenter, Inscribed Circle, Tangency Points, Perpendicular, 90 Degrees, Angle Bisector.

Geometry Problem 1268.
Triangle, Exterior Angle Bisector, Circumcircle, Circle, Chord, Parallel, Concyclic Points, Cyclic Quadrilateral.

Geometry Problem 1267.
Triangle, Incircle, Excircle, Circle, Tangency Points, Perpendicular, 90 Degrees, Parallelogram.

Geometry Problem 1266.
Triangle, Excircle, Circle, Tangency Points, Perpendicular, 90 Degrees, Angle Bisector.

Geometry Problem 1265.
Triangle, Incircle, Circle, Tangency Points, Perpendicular, 90 Degrees, Angle Bisector.

Geometry Problem 1264.
Triangle, Exterior Angle Bisector, Circumcircle, Circle, Perpendicular, 90 Degrees, Concurrent Lines.

Geometry Problem 1263.
Triangle, Medians, 90 Degrees, Perpendicular.

Geometry Problem 1262.
Isosceles Triangle, Altitude, Medians, 90 Degrees, Perpendicular.

Geometry Problem 1261.
Cyclic Quadrilateral, Circle, Diameter, Midpoint, Measurement.

Geometry Problem 1260.
Triangle, Internal Angle Bisector, Circumcircle, Circle, Perpendicular, 90 Degrees, Concurrent Lines.

Geometry Problem 1259.
Triangle, Circumcircle, Circle, Diameter, Parallel Lines.

Geometry Problem 1257.
Triangle, Altitude, Perpendicular, 90 Degree, Measurement.

Geometry Problem 1256.
Parallelogram, Angle Bisector, Measurement.

Geometry Problem 1255.
Right Triangle, Angle, 90 Degrees, Perpendicular, Collinear Points.

Geometry Problem 1253.
Triangle, Orthocenter, Circle, Circumcircle, Altitude, Perpendicular, 90 Degree, Concurrency.

Geometry Problem 1252.
Triangle, Circle, Circumcircle, Altitude, Area, Hexagon, Perpendicular, 90 Degrees. Mind Map.

Geometry Problem 1251.
Triangle, Circle, Diameter, Perpendicular, 90 Degrees.

Geometry Problem 1249.
Cyclic Quadrilateral, Circle, Triangle, Circumcircle, Angle Bisector, Parallel Lines, Area.

Geometry Problem 1248.
Triangle, Circumcircle, Circle, Diameter, Orthocenter, Altitude, Parallel Lines.

Geometry Problem 1247.
Triangle, Circumcircle, Orthocenter, Altitude, Perpendicular, Midpoint.

Geometry Problem 1246.
Triangle, Orthocenter, Altitude, Midpoint, Perpendicular.

Geometry Problem 1240
Triangle, Circle, Diameter, Circumcircle, Circumcenter, Perpendicular. Mobile Apps.

Geometry Problem 1238
Square, Equilateral Triangle, Metric Relations. Mobile Apps.

Geometry Problem 1237
IMO 2016, Problem 1, Triangle, Congruence, Parallel Lines, Midpoint, Concurrency.

Geometry Problem 1235
Triangle, Cevians, Concurrency, Circle, Circumcircle.

Geometry Problem 1234
Quadrilateral, 60 Degrees, Midpoint, Congruence, Cyclic Quadrilateral, Concyclic Points.

Geometry Problem 1233
Triangle, Euler Line, Orthic Axis, Perpendicular, 90 Degrees, Orthic Triangle.

Geometry Problem 1232
Triangle, Altitudes, Orthic Triangle, Collinearity, Orthic Axis.

Geometry Problem 1231
Triangle, Orthocenter, Incenter, Circumcenter, Angle Bisector, Center, Circle.

Geometry Problem 1230
Quadrilateral, 60 Degrees, Congruence, Metric Relations.

Geometry Problem 1229
Three Tangent Circles, Midpoint, Common Tangent Line, 3-4-5 Right Triangle.

Geometry Problem 1227
Triangle, Circumcircle, Angle Bisector, Concyclic Points, Cyclic Quadrilateral.