Constructing a line perpendicular to a given line and through a point not on the line is one of the most important constructions in geometry. This process is known as dropping a perpendicular, because ...

Drag points A, B, and P to change the relationship between these points. Use the buttons, in order, to demonstrate how a line is constructed perpendicular to a given line and through a given point.

Equation of altitudes and perpendicular bisectors Now use the information you already have about finding the equation of a line and apply it to the dashed lines shown in these triangles.

Angles in a triangle add up to 180° and quadrilaterals add up to 360°. Angles can be calculated inside semicircles and circles, as well as with perpendicular bisectors and tangents.

Allan Berele, Stefan Catoiu, Area and Perimeter Bisecting Lines of a Triangle, The College Mathematics Journal, Vol. 47, No. 1 (January 2016), pp. 19-28 ...