The same argument would hold for tan(pi/2).
I don't say the result 'NaN' is wrong,
but I thought,
tan(pi*x) and tanpi(x) should give the same result.
Hans Werner
On Fri, Sep 9, 2016 at 8:44 PM, William Dunlap <wdunlap at tibco.com> wrote:
It should be the case that tan(pi*x) != tanpi(x) in many cases - that is
it was added. The limits from below and below of the real function
tan(pi*x) as x approaches 1/2 are different, +Inf and -Inf, so the limit
not well defined. Hence the computer function tanpi(1/2) ought to
Not-a-Number.
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Fri, Sep 9, 2016 at 10:24 AM, Hans W Borchers <hwborchers at gmail.com>
wrote:
As the subject line says, we get different results for tan(pi/2) and
tanpi(1/2), though this should not be the case:
[1] NaN
Warning message:
In tanpi(1/2) : NaNs produced
By redefining tanpi with sinpi and cospi, we can get closer:
> tanpi <- function(x) sinpi(x) / cospi(x)
> tanpi(c(0, 1/2, 1, 3/2, 2))
[1] 0 Inf 0 -Inf 0
Hans Werner