text: var assert = require('assert'),
      error = require('../../../lib/error/index'),
      math = require('../../../index'),
      approx = require('../../../tools/approx'),
      pi = math.pi,
      complex = math.complex,
      matrix = math.matrix,
      unit = math.unit,
      tan = math.tan,
      piBigmath = math.create({number: 'bignumber', precision: 21}),
      bigmath = math.create({precision: 20}),
      Big = bigmath.bignumber,
      bigTan = bigmath.tan;
  
  describe('tan', function() {
    it('should return the tangent of a boolean', function () {
      approx.equal(tan(true), 1.55740772465490);
      approx.equal(tan(false), 0);
    });
  
    it('should return the tangent of null', function () {
      approx.equal(tan(null), 0);
    });
  
    it('should return the tangent of a number', function() {
      approx.equal(tan(0), 0);
      approx.equal(tan(pi*1/4), 1);
      approx.equal(tan(pi*1/8), 0.414213562373095);
      assert.ok(tan(pi*2/4) > 1e10);
      approx.equal(tan(pi*3/4), -1);
      approx.equal(tan(pi*4/4), 0);
      approx.equal(tan(pi*5/4), 1);
      assert.ok(tan(pi*6/4) > 1e10);
      approx.equal(tan(pi*7/4), -1);
      approx.equal(tan(pi*8/4), 0);
    });
  
    it('should return the tangent of a bignumber', function() { 
      var bigPi = piBigmath.pi;
      var bigTau = piBigmath.tau;
  
      assert.deepEqual(bigTan(Big(0)), Big(0));
      assert.deepEqual(bigTan(Big(-1)), Big('-1.5574077246549022305'));
  
      assert.deepEqual(bigTan(bigPi.div(8)).toString(), '0.4142135623730950488');
      assert.deepEqual(bigTan(bigPi.div(4)).toString(), '1');
      assert.ok(!bigTan(bigPi.div(2)).isFinite());
      assert.ok(!bigTan(bigPi.times(3).div(2)).isFinite());
      assert.ok(bigTan(bigPi.times(2)).isZero());
      assert.ok(bigTan(bigPi.times(4)).isZero());
      assert.ok(bigTan(bigTau).isZero());
      assert.ok(bigTan(bigTau.times(2)).isZero());
  
      /* Passes with an extra digit of pi! */
      assert.deepEqual(bigTan(bigPi.times(3).div(4)).toString(), '-1');
      assert.ok(bigTan(bigPi).isZero());
      assert.deepEqual(bigTan(bigPi.times(5).div(4)).toString(), '1');
      assert.deepEqual(bigTan(bigPi.times(7).div(4)).toString(), '-1');
    });
  
    it('should return the tangent of a complex number', function() {
      var re = 0.00376402564150425,
          im = 1.00323862735360980;
      approx.deepEqual(tan(complex('2+3i')), complex(-re, im));
      approx.deepEqual(tan(complex('2-3i')), complex(-re, -im));
      approx.deepEqual(tan(complex('-2+3i')), complex(re, im));
      approx.deepEqual(tan(complex('-2-3i')), complex(re, -im));
      approx.deepEqual(tan(complex('i')), complex(0, 0.761594155955765));
      approx.deepEqual(tan(complex('1')), complex(1.55740772465490, 0));
      approx.deepEqual(tan(complex('1+i')), complex(0.271752585319512, 1.083923327338695));
    });
  
    it('should return the tangent of an angle', function() {
      approx.equal(tan(unit(' 60deg')), math.sqrt(3));
      approx.equal(tan(unit('-135deg')), 1);
    });
  
    it('should throw an error if called with an invalid unit', function() {
      assert.throws(function () {tan(unit('5 celsius'))});
    });
  
    it('should throw an error if called with a string', function() {
      assert.throws(function () {tan('string')});
    });
  
    var tan123 = [1.557407724654902, -2.185039863261519, -0.142546543074278];
  
    it('should return the tan of each element of an array', function() {
      approx.deepEqual(tan([1,2,3]), tan123);
    });
  
    it('should return the tan of each element of a matrix', function() {
      approx.deepEqual(tan(matrix([1,2,3])), matrix(tan123));
    });
  
    it('should throw an error in case of invalid number of arguments', function() {
      assert.throws(function () {tan()}, error.ArgumentsError);
      assert.throws(function () {tan(1, 2)}, error.ArgumentsError);
    });
  
  });
  