## Perl - 74 bytes ##

<!-- language-all: lang-perl -->

    $~=<>=~$"+$'*2;$_=1-$_*$`/$~/--$~*$`for($,,$;)x$';printf'%.8f
    'x2,$`*$,,$;

Or, counting command line options as 1 byte each, **72 bytes**:

    #!perl -n
    $~=/ /+$'*2;$_=1-$_*$`/$~/--$~*$`for($,,$;)x$';printf'%.8f
    'x2,$`*$,,$;

Sample usage:

    $ echo 5 3 | perl sin-cos.pl
    10.20833333
    14.54166667

    $ echo 9.26 50 | perl sin-cos.pl
    0.16403330
    -0.98645480

    $ echo 6.54 12 | perl sin-cos.pl
    0.25398611
    0.96714730

    $ echo 5 1 | perl sin-cos.pl
    5.00000000
    1.00000000