which of his works brought him the fame?
His book "Philosophiæ Naturalis Principia Mathematica" laid the foundations of classical mechanics.
Isaac Newton
 His book "Philosophiæ Naturalis Principia Mathematica" ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations of classical mechanics.
an isosceles triangle has two sides of equal length UNANSWERABLE how did it gat the name? "Isosceles" is made from the Greek roots "isos" (equal) and "skelos" (leg). how can one find it's area? The same area formula can also be derived from Heron's formula for the area of a triangle from its three sides. where all can it be applied? Celestial mechanics what is it about? It  is the branch of astronomy that deals with the motions of objects in outer space. who all have proposed studies on it? Isaac Newton, Gottfried Leibniz, Pierre-Simon Laplace when was the first scientist born? 25 December 1642 where? Lincolnshire what were his famous findings? He formulated the laws of motion and universal gravitation. what does the latter mean? It  is usually stated as that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. how is he related to the field of optics? Newton lectured on optics. During this period he investigated the refraction of light, demonstrating that the multicoloured spectrum produced by a prism could be recomposed into white light by a lens and a second prism.
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Isaac Newton [SEP] Introduction
Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, theologian, and author (described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time and as a key figure in the scientific revolution. His book "Philosophiæ Naturalis Principia Mathematica" ("Mathematical Principles of Natural Philosophy"), first published in 1687, laid the foundations of classical mechanics. Newton also made seminal contributions to optics, and shares credit with Gottfried Wilhelm Leibniz for developing the infinitesimal calculus. In "Principia", Newton formulated the laws of motion and universal gravitation that formed the dominant scientific viewpoint until it was superseded by the theory of relativity.