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!