The figure shows the vertical angles BAC and DAE. F and G are the orthocenters of trianglers ABC and ADE, respectively. If M and N are the midpoints of BE and CD, respectively, prove that MN and FG are perpendicular.

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GeoGebra is free and multi-platform dynamic mathematics software for all levels of education that joins geometry, algebra, tables, graphing, statistics and calculus application, intended for teachers and students. Many parts of GeoGebra have been ported to HTML5.

Geometry Problems

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Ten problems: 1411-1420

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Triangle

Altitude

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