Wallace Line by the Sahul Shelf to New Guinea. The biogeographic boundary known as Lydekker's Line, which separates the eastern edge of Wallacea from the Australian region, has a similar origin to the Wallace line. During ice age glacial advances, when the , both Asia and Australia were united with what are now islands on their respective continental shelves as continuous land masses, but the deep water between those two large continental shelf areas was, for over 50 million years, a barrier that kept the flora and fauna of Australia separated from those of Asia. Wallacea consists of islands that were not
Simson line that formula_2. formula_3 is a cyclic quadrilateral, so formula_4. formula_5 is a cyclic quadrilateral (Thales' theorem), so formula_6. Hence formula_7. Now formula_8 is cyclic, so formula_9. Therefore formula_10. Simson line In geometry, given a triangle "ABC" and a point "P" on its circumcircle, the three closest points to "P" on lines "AB", "AC", and "BC" are collinear. The line through these points is the Simson line of "P", named for Robert Simson. The concept was first published, however, by William Wallace in 1797. The converse is also true; if the three closest points to "P" on three lines are collinear,