Quote by Joseph-Louis Lagrange
"The beauty of a mathematical proof is that once demonstrated, it is eternal."
More from Joseph-Louis Lagrange
"The true system of the world has been recognised, last, in the masterly work of Newton on the Mathematical Principles of Natural Philosophy."
"I have turned my mind to the great problems of mathematics."
"The study of mathematics is like climbing a high mountain."
"Nature laughs at the difficulties of calculus."