under a curious financial with johann,assembled in 1969 into the first calculus textbook. It was in this way that the familar method of evaluating the indeterminate form 0/0 became incorrectly known,in later calculus texts, as l'Hospital's rule. Johann Bernoulli wrote on awide variety of topics, including opical phenomena connected with reflection and refraction, the determination of the orthogonal trajectories of families of curves, rectification of curves and quadrature of areas by series, analytical trigonometry, the exponential calculus, and other subjects.