mathjs/lib/function/trigonometry/cosh.js

'use strict';

var bigCosh = require('../../util/bignumber').cosh_sinh_csch_sech;

function factory (type, config, load, typed) {
  var collection = load(require('../../type/matrix/collection'));

  /**
   * Calculate the hyperbolic cosine of a value,
   * defined as `cosh(x) = 1/2 * (exp(x) + exp(-x))`.
   *
   * For matrices, the function is evaluated element wise.
   *
   * Syntax:
   *
   *    math.cosh(x)
   *
   * Examples:
   *
   *    math.cosh(0.5);       // returns Number 1.1276259652063807
   *
   * See also:
   *
   *    sinh, tanh
   *
   * @param {Number | BigNumber | Boolean | Complex | Unit | Array | Matrix | null} x  Function input
   * @return {Number | BigNumber | Complex | Array | Matrix} Hyperbolic cosine of x
   */
  var cosh = typed('cosh', {
    'number': _cosh,

    'Complex': function (x) {
      var ep = Math.exp(x.re);
      var en = Math.exp(-x.re);
      return new type.Complex(Math.cos(x.im) * (ep + en) / 2, Math.sin(x.im) * (ep - en) / 2);
    },

    'BigNumber': function (x) {
      return bigCosh(x, type.BigNumber, false, false);
    },

    'Unit': function (x) {
      if (!x.hasBase(type.Unit.BASE_UNITS.ANGLE)) {
        throw new TypeError ('Unit in function cosh is no angle');
      }
      return _cosh(x.value);
    },

    'Array | Matrix': function (x) {
      return collection.deepMap(x, cosh);
    }
  });

  return cosh;
}

/**
 * Calculate the hyperbolic cosine of a number
 * @param {number} x
 * @returns {number}
 * @private
 */
function _cosh(x) {
  return (Math.exp(x) + Math.exp(-x)) / 2;
}

exports.name = 'cosh';
exports.factory = factory;