Logic Scheme of Main Results in Euclidean Geometry Supplements. Opposite angles. Basic definitions Corresponding angles, Alternate angles Sum of angles in a triangle is 180 deg. Euclid’s fifth postulate Parallelogram properties. Rectangle Properties. Rhombus properties. Midline properties Properties of medians Centroid Isosceles triangles Properties of angle bisectors Incentre SSS SAS, ASA Congruent triangles Properties of segment bisectors Circumcentre Pythagora’s theorem Properties of heights Orthocentre Properties of circles: angles, secants, tangents