My conclution is that the sum of the 4 angles of each quadrilateral is of 360°. The angle of the sum of all the angles of a quadrilateral is of 180° more than the angle of sum of the 3 angles of a triangle.
Euclid Prop 1 (Mr Ben)
Fundamental Theorem quiz reinforce
CAST and Cosine Graph
Double integral (visual)
Perpendicular bisectors of a triangle
Derivatives of y=sinx and y=cosx