Output an Animated Trigonometry Circle
Mathematica, 142 bytes

Graphics[{Circle[],Line/@{{{c=Cos@t,0},{c,s=Sin@t},{0,s}},{{0,0},{1/c,0},{0,1/s},{0,0},{c,s}}},},PlotRange-&gt;{r={-2,2},r}]~Animate~{t,0.01,2Pi}


I'm plotting for angles between 0.01 and 2π which conveniently skips any angles where one of the lines would become actually infinite. You can make a GIF from it by replacing Animate with Table, adding a step width of 0.1 say and then using Export on the result:



So I got a bit bored and thought I'd give the full-blown thing a go (with all lines and colours). I omitted the labels, because they are really annoying to position and just clutter everything up.

Animate[
  c = Cos@t;
  s = Sin@t;
  h = Sign@c;
  v = Sign@s;
  i = .1 h;
  j = .1 v;
  Graphics[{
    Thick,
    Circle[],
    Line /@ {{{c, -s}, {0, 0}, {c, s}}, {{-i, 0}, {-i, j}, {0, 
        j}}, {{-i + c, 0}, {-i + c, j}, {c, j}}, {{c - .1 s, 
        s + .1 c}, {1.1 c - .1 s, 1.1 s + .1 c}, 1.1 {c, s}}},
    Circle[{0, 0}, 0.1, {t, Round[t, Pi]}],
    Blue,
    Line /@ {{{0, 0}, {c, 0}}, {{0, s}, {c, s}}},
    Red,
    Line /@ {{{0, 0}, {0, s}}, {{c, 0}, {c, s}}},
    Darker@Green,
    Line[{{c, 0}, {h, 0}}],
    Cyan,
    Line[{{0, s}, {0, v}}],
    Lighter@Lighter@Magenta,
    Line[{{h, 0}, {1/c, 0}}],
    Darker@Darker@Green,
    Line[{{0, v}, {0, 1/s}}],
    Orange,
    Line[{{0, 1/s}, {c, s}}],
    Lighter@Brown,
    Line[{{1/c, 0}, {c, s}}],
    Gray,
    Line[{{c, 0}, {c, -s}}],
    Lighter@Gray,
    Line[{{c, s}, {h, 0}}],
    Lighter@Pink,
    Line /@ {{{-.45 h, 0}, {-.55 h, 0}}, {{-.45 h, 1/s}, {-.55 h, 
        1/s}}},
    Arrowheads[{-.05, .05}],
    Arrow[{{-.5 h, 0}, {-.5 h, 1/s}}],
    Darker@Cyan,
    Line /@ {{{0, -.45 v}, {0, -.55 v}}, {{1/c, -.45 v}, {1/
         c, -.55 v}}},
    Arrow[{{0, -.5 v}, {1/c, -.5 v}}],
    Dashed,
    Black,
    Line[{{c, s}, 1.3 {c, s}}],
    Lighter@Pink,
    Line /@ {{{0, 0}, {-.5 h, 0}}, {{0, 1/s}, {-.5 h, 1/s}}},
    Darker@Cyan,
    Line /@ {{{0, 0}, {0, -.5 v}}, {{1/c, 0}, {1/c, -.5 v}}}
    }, PlotRange -&gt; {r = {-2, 2}, r}],
  {t, 0.01, 2 Pi}
  ];


Enjoy!



And because this is still a code-golf question I golfed this down as well, to see how short I could get it. Currently, 719 bytes:

Graphics[{Thick,Arrowheads@{-.05,.05},(z=Circle)[],(n=Line)/@{{p={c=Cos@t,s=Sin@t},o={0,0},{c,-s}},{-{i=.1(h=Sign@c),0},{-i,j=.1(v=Sign@s)},{0,j}},{{-i+c,0},{-i+c,j},{c,j}},{p+(q={-.1s,.1c}),1.1p+q,1.1p}},z[o,0.1,{t,Round[t,Pi]}],{e=Dashed,n[{p,1.3p}]},Blue,n/@{{o,a={c,0}},{b={0,s},p}},Red,n/@{{o,b},{a,p}},g=(d=Darker)@Green,n@{a,{h,0}},y=Cyan,n@{b,{0,v}},(l=Lighter)@l@Magenta,n@{{h,0},f={1/c,0}},d@g,n@{{0,v},u={0,1/s}},Orange,n@{u,p},l@Brown,n@{f,p},r=Gray,n@{a,{c,-s}},l@r,n@{p,{h,0}},l@Pink,n/@{q={{-.45h,0},{-.55h,0}},{u,u}+q},Arrow@{q={-.5h,0},u+q},{e,n/@{{o,q},{u,u+q}}},d@y,n/@{q={{0,-.45v},{0,-.55v}},{f,f}+q},Arrow@{q={0,-.5v},f+q},{e,n/@{{o,q},{f,f+q}}}},PlotRange-&gt;{r={-2,2},r}]~Animate~{t,0.01,2Pi,0.05}