test_tan = ->
  run_test [
    "tan(x)",
    "tan(x)",

    "tan(-x)",
    "-tan(x)",

    "tan(b-a)",
    "-tan(a-b)",

    # check against the floating point math library

    "f(a,x)=1+tan(float(a/360*2*pi))-float(x)+tan(a/360*2*pi)-x",
    "",

    "f(0,0)",      # 0
    "1.0",

    "f(180,0)",      # 180
    "1.0",

    "f(360,0)",      # 360
    "1.0",

    "f(-180,0)",      # -180
    "1.0",

    "f(-360,0)",      # -360
    "1.0",

    "f(45,1)",      # 45
    "1.0",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(135,-1)",      # 135
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(225,1)",      # 225
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(315,-1)",      # 315
    "1.000000...",

    "f(-45,-1)",      # -45
    "1.0",

    "f(-135,1)",      # -135
    "1.0",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-225,-1)",      # -225
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-315,1)",      # -315
    "1.000000...",

    "f(30,sqrt(3)/3)",    # 30
    "1.0",

    "f(150,-sqrt(3)/3)",    # 150
    "1.0",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(210,sqrt(3)/3)",    # 210
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(330,-sqrt(3)/3)",    # 330
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-30,-sqrt(3)/3)",    # -30
    "1.000000...",

    "f(-150,sqrt(3)/3)",    # -150
    "1.0",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-210,-sqrt(3)/3)",    # -210
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-330,sqrt(3)/3)",    # -330
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(60,sqrt(3))",    # 60
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(120,-sqrt(3))",    # 120
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(240,sqrt(3))",    # 240
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(300,-sqrt(3))",    # 300
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-60,-sqrt(3))",    # -60
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-120,sqrt(3))",    # -120
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-240,-sqrt(3))",    # -240
    "1.000000...",

    # this should really be 1.0 , however
    # we have errors doing the calculations so
    # we don't get to that exact 1.0 float
    "f(-300,sqrt(3))",    # -300
    "1.000000...",

    "f=quote(f)",
    "",

    "tan(arctan(x))",
    "x",

    # check the default case

    "tan(1/12*pi)",
    "tan(1/12*pi)",
  ]