mirror of https://github.com/jkjoy/sunpeiwen.git
31 lines
593 B
JavaScript
31 lines
593 B
JavaScript
|
var utils = require('../utils')
|
||
|
|
, nodes = require('../nodes');
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Return the tangent of the given `angle`.
|
||
|
|
*
|
||
|
|
* @param {Unit} angle
|
||
|
|
* @return {Unit}
|
||
|
|
* @api public
|
||
|
|
*/
|
||
|
|
|
||
|
|
function tan(angle) {
|
||
|
|
utils.assertType(angle, 'unit', 'angle');
|
||
|
|
|
||
|
|
var radians = angle.val;
|
||
|
|
|
||
|
|
if (angle.type === 'deg') {
|
||
|
|
radians *= Math.PI / 180;
|
||
|
|
}
|
||
|
|
|
||
|
|
var m = Math.pow(10, 9);
|
||
|
|
|
||
|
|
var sin = Math.round(Math.sin(radians) * m) / m
|
||
|
|
, cos = Math.round(Math.cos(radians) * m) / m
|
||
|
|
, tan = Math.round(m * sin / cos ) / m;
|
||
|
|
|
||
|
|
return new nodes.Unit(tan, '');
|
||
|
|
}
|
||
|
|
tan.params = ['angle'];
|
||
|
|
module.exports = tan;
|