[摘]C#使用非内部数学函数

以下为非内部数学函数的列表，这些函数皆可由内部数学函数导出：

正切 (Sec(x))= 1 / Cos(x)  
余切 (Csc(x))= 1 / Sin(x)  
余切 (Ctan(x))= 1 / Tan(x) 
反正弦 (Asin(x))= Atan(x / Sqrt(-x * x + 1)) 
反余弦 (Acos(x))= Atan(-x / Sqrt(-x * x + 1)) + 2 * Atan(1)  
反正割 (Asec(x))= 2 * Atan(1) – Atan(Sign(x) / Sqrt(x * x – 1))  
反余割 (Acsc(x))= Atan(Sign(x) / Sqrt(x * x – 1))  
反余切 (Acot(x))= 2 * Atan(1) - Atan(x)  
双曲正弦 (Sinh(x))= (Exp(x) – Exp(-x)) / 2 
双曲余弦 (Cosh(x))= (Exp(x) + Exp(-x)) / 2 
双曲正切 (Tanh(x))= (Exp(x) – Exp(-x)) / (Exp(x) + Exp(-x))  
双曲正割 (Sech(x))= 2 / (Exp(x) + Exp(-x))  
双曲余割 (Csch(x))= 2 / (Exp(x) – Exp(-x))  
双曲余切 (Coth(x))= (Exp(x) + Exp(-x)) / (Exp(x) – Exp(-x))  
反双曲正弦 (Asinh(x))= Log(x + Sqrt(x * x + 1))  
反双曲余弦 (Acosh(x))= Log(x + Sqrt(x * x – 1))  
反双曲正切 (Atanh(x))= Log((1 + x) / (1 – x)) / 2  
反双曲正割 (AsecH(x))= Log((Sqrt(-x * x + 1) + 1) / x)  
反双曲余割 (Acsch(x))= Log((Sign(x) * Sqrt(x * x + 1) + 1) / x)  
反双曲余切 (Acoth(x))= Log((x + 1) / (x – 1)) / 2