Hello and welcome to HD Calcs I'm Rick and today  we have a quick look at how to find trig functions  

on the Casio FX-991 MS calculator. To do this  we'll be using the sine cosine and tangent keys  

located along here, Sin Cos and Tan, as well as  the shift key looks like this and is located here,  

and the X to the power of negative 1 or X inverse  key that looks like this and is located up here.  

Getting started these examples will be in degrees  so we want to make sure our calculator is set to  

degrees. We can confirm this by seeing a little  D in the top row there, and if we don't see that  

what we can do is change our calculator to degrees  mode by pressing the mode key 1 2 3 4 times until  

we see this screen. Deg Rad and Gra which stands  for Degrees, Radians and Gradients. Like I said we  

want to be in degrees so we select 1 and now we  should have that D on the top screen there. All  

right, if we're just doing the basics like say the  sine of 30 degrees we would enter it as we would  

write it so we press sine 30 and equals gives us  a result of 0.5. Cosine of 30 again cos 30 equals  

0.8660, and tangent of 30, Tan 30 equals 0.5774. Easy enough but what if we wanted to find  

functions like Cosecant, Secant and Cotangent?  Well to do this what we actually have to do is  

inverse the result of its corresponding function.  So if we wanted to say find the cosecant of 30  

degrees first we have to find the sine of 30,  sine 30, press equals and we're back to our 0.5  

and then we want to inverse this with this X to  the power negative 1 or X inverse key, and press  

equals. And we see we get 2, The cosecant of 30  degrees is equal to 2. Secant, same thing but done  

with cos, so if we go cos 30 equals, and then  inverse that, equals we get a secant of 1.1547  

etc. And with tangent, tan of 30 equals, inverse  that to get our cotangent which is 1.7321 etc.

What about arcsin, arccos and arctan? Well these  are actually represented by the sin minus 1,  

cos minus 1, and tan minus 1 that are these  shift functions on our sin cos and tan keys.  

And we use these to go from the result of  say, sin 30 degrees, which gave us 0.5,  

back to the degrees. So if we wanted to say  find out how many degrees we used to get zero  

point five we would use shift sin, so we get sin  minus 1, .5 and equals and we see this brings us  

back to 30 degrees. Same thing with arccos,  if we press shift cos and then remember we've  

rounded this to 0.8660. So 0.8660 equals, this  brings us back to what would round to 30 degrees.

Again with tangent remember we got 0.5774  so if we gi shift tan, here is our arctan.

0.5774 equals, this brings us  back to our rounded 30 degrees.

All right I hope this helps out there  everybody and good luck on those tests!