Thursday, December 6, 2012

`lim_(x->0^(-)) (cothx)` Find the limit

By definition, hyperbolic cotangent `coth(x)` is equal to `(cosh(x))/(sinh(x)),` which is equal to  `(e^x + e^(-x))/(e^x - e^(-x)).`


When `x -> 0^-,` both `e^x` and `e^(-x)` tend to `1.` But while `e^x -> 1^-,`  `e^(-x) = 1/e^x -> 1+.` Therefore the numerator tends to `1 + 1 = 2,` and the denominator tends to  `1^(-) - 1^+ = 0^-.`


And finally `2/0^-` gives the limit of `-oo.` This is the answer.

No comments:

Post a Comment

Thomas Jefferson's election in 1800 is sometimes called the Revolution of 1800. Why could it be described in this way?

Thomas Jefferson’s election in 1800 can be called the “Revolution of 1800” because it was the first time in America’s short history that pow...