# Thread: Using Calc to find Inverse

1. ## Using Calc to find Inverse

I'm using a Sci Calc to find Inverse functions... I have no problem with sin cos tan...But I can't seem to get the right answer to, Y=Cot^-1(-.92170128)....I enter it as Tan^-1(1/-.92170128) and get -.826120119....The answer is supposed to be 2.3154724.....Calc must be in Rad...Can anyone tell my what my mistake is

2. Originally Posted by Brndo4u
I'm using a Sci Calc to find Inverse functions... I have no problem with sin cos tan...But I can't seem to get the right answer to, Y=Cot^-1(-.92170128)....I enter it as Tan^-1(1/-.92170128) and get -.826120119....The answer is supposed to be 2.3154724.....Calc must be in Rad...Can anyone tell my what my mistake is
$\displaystyle tan^{-1}$ of your calculator always gives you an answer in the range $\displaystyle (-\pi/2;+\pi/2)$, but since $\displaystyle tan$ has period $\displaystyle \pi$ you may add any integral multiple of $\displaystyle \pi$ to get all the other (infinitely many) angles for which $\displaystyle \tan$ has the exact same value. - Therefore: add or subtract $\displaystyle \pi$ as many times as necessary to get an angle in the required range.