math/cmplx: hyperbolic sinh, cosh and tanh give wrong result for Inf input #29320
Description
What version of Go are you using (go version)?
$ go version go version go1.11.4 linux/amd64
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (go env)?
go env Output
$ go env GOHOSTARCH="amd64" GOHOSTOS="linux" GOOS="linux"
What did you do?
Run the code at https://play.golang.org/p/8dz30xSTLdI.
Notice that sinh(inf) and cosh(inf) are inf, and tanh(inf) is 1.
What did you expect to see?
sinh((+Inf+Infi)) -> (+Inf+Infi)
cosh((+Inf+Infi)) -> (+Inf+Infi)
tanh((+Inf+Infi)) -> (1+0i)
What did you see instead?
sinh((+Inf+Infi)) -> (NaN+NaNi)
cosh((+Inf+Infi)) -> (NaN+NaNi)
tanh((+Inf+Infi)) -> (NaN+NaNi)