Method atan2

__test__/theorem.js:405–413

(x, y)

  	return result.length == 1 ? result[0] : result
  }
  atan2(x, y) {
  	x = [BigNumber(x).toNumber()]
  	y = [BigNumber(y).toNumber()]
  	let result = []
      for (var i = 0; i < x.length; i++) {
      	result.push(Math.atan2(x[i], y[i]))
      }
  	return result.length == 1 ? result[0] : result
  }
  atanh(n) {
  	if (typeof n != 'object') {
  		n = BigNumber.isBigNumber(n) == true ? n.toNumber() : n