Geometry classes, Problem 222. Viviani's Theorem, Equilateral Triangle, Exterior Point. Math teacher Master Degree. College, SAT Prep. Elearning, Online math tutor, LMS.

Problem 222. Viviani's Theorem, Equilateral Triangle, Point, Altitude, Distance

For a given point D outside an equilateral triangle ABC, the sum of the distances DE and DF minus DG from the point D to the sides BC, AB and AC respectively is equal to the altitude of the triangle. View or post a solution

Viviani theorem exterior point

The theorem is named for Vincenzo Viviani (1622-1703), a pupil of Galileo and Torricelli, who is also remembered for a reconstruction of a book on the conic sections of Apollonius and for finding a way of trisecting an angle through the use an equilateral hyperbola.