Arctan

Arctan is the same as inverse tan.

 

You use it to find an angle.

More info here.

 

http://www.mathsisfun.com/algebra/trig-inverse-sin-cos-tan.html

Arctan x   means 'the angle whose tangent is x'      As does arcsinx means 'the angle whose sine is x'.    When you see arctan,arcsin,arccos,  you are looking at expressions for angles.    -    Here's a handy thing to know: --

 

 

If you know that arctan x = 1/2 ,for example,you can draw the right-angled triangle with opposite side length 1,adjacent side 2  and find all sides and angles.  As you can if you were given similar expressions for arcsin etc.