Why does my TI-30X IIS calculator give the wrong cos, sin, and tan answers?

Question

I just noticed that my graphing calculator (TI-nspire) was giving the wrong trig function answers. Someone told me to just go to mode and change from radians to degrees. So now that that is fixed, I notice that my TI-30X IIS calculator gives the answers as if I'm lookinh for functions of radians as well. I can't find a mode button and this is really aggravating me. Like I know this calculator can't just be dumb (I did hear that it got a recall on giving wrong answers though). Oh and also, when I do put in a equation like cos (pi/2)... it says .999624217, but my teacher says that cos(pi/2) is 0. Agh! Any help would be greatly appreciated.

Answer 1

Yup you're getting into trouble over degrees and radians.



You fixed the "problem" by changing radians to degrees now you're getting your answers in degrees.



cos(pi/2 degrees) really is .999624217 but cos (pi/2 radians) is zero. This is because pi/2 radians is 90 degrees.



If you try typing cos (pi/2) into your TI-30X IIS that is still stuck on radians you'll get the answer as 0, if you type the same thing into your TI-nspire which is set to degrees you'll get .999624217



You are wrong though - calculators are very dumb just like computers they give you the answer to the question you typed in, they don't intelligently guess what they think you probably meant to type in.



You don't need to find the mode button on the TI-30X IIS right next to the blue 2nd button is a button marked DRG.



This button DRG stands for Degrees Radians Gradient which are three different ways of measuring angles. Simply pressing the DRG button should change from Radians to either Degrees or Gradient. If you look at the display you'll notice a little RAD on your display underneath the answer. Pressing the DRG button will change it to either GRA or DEG. If you want to input your angle in degrees you must press the DRG button until the DEG is showing, if you want to enter your angle as radians you need to have the RAD showing and if you want to input the slope as a gradient have the GRA lit up.



Hope this helps.

Answer 2

Ti 30 Graphing Calculator

Answer 3

You only get 0.999624217 if you put the value of pi/2 when the calculator is incorrectly set to Degrees instead of radians; as I proved on my calc which gave: 0.9996242169. Swich to radian mode and it will give you zero. I suspect you have not got it working in the correct mode and that is why you are having all this trouble.



You need to press the 2nd button followed by the button under DEL that looks like degrees mins and sec. repeately pressing this button will rotate you though deg/rad/grad. look for the mode of operation in the display D/R/G (well, on my calulator anyway) Grad is special as it used 100 degrees in a right angle i think its used by serveyors.