Analysis of information sources in references of the Wikipedia article "双曲函数" in Chinese language version.
We also owe to Lambert the first systematic development of the theory of hyperbolic functions and, indeed, our present notation for these functions.
That the area of a hyperbolic triangle is proportional to its angle defect first appeared in Lambert's monograph Theorie der Parallellinien, which was published posthumously in 1786.
That the area of a hyperbolic triangle is proportional to its angle defect first appeared in Lambert's monograph Theorie der Parallellinien, which was published posthumously in 1786.
