use more accurate algorithm for tan. from fdlibm 5.3:
authormartynas <martynas@openbsd.org>
Sun, 20 Jul 2008 13:03:13 +0000 (13:03 +0000)
committermartynas <martynas@openbsd.org>
Sun, 20 Jul 2008 13:03:13 +0000 (13:03 +0000)
commitee391e4f46b99a88279849721d791309b505a2b9
tree2225a9a96be3e3c5959d0070d9388cbc0f237068
parentd9c89e4ca5b8ffba3ff406551fe3de5edefe2586
use more accurate algorithm for tan.  from fdlibm 5.3:
>     2. k_tan.c error was > 1 ulp target for FDLIBM
>         5.2: Worst error at least 1.45 ulp at
>         tan(1.7765241907548024E+269) = 1.7733884462610958E+16
>         5.3: Worst error 0.96 ulp
ok millert@
lib/libm/src/k_tan.c