Solving Basic Trig

[CmpFreak88]

Alright so I've got my TI-89 and I'm working through my first homework assignment with it, woohoo! And I get to a 3,4,5 right triangle, so I try and use the calculator to solve one of the angles, so I go ahead and input cos^-1(3/5) and then it just spits the same thing back out at me! So I try it with just cos(3/5) and it does the same! Same with tan and sin! Now... I now this calculator does everything, but how do I do this? I think what I'm going to have to do is input approx(cos^-1(3/5)) in order to get my answer? That's kinda lame if you ask me...

[lilkev715]

You have to set your calculator to Degree mode first, it is set to Radian mode by default.

 

Or you can convert radians to degrees, or vice versa.

radians--> degrees: (180)/(pie)(radians)

degrees--> radians: (pie)(radians)/(180)

 

Hope this helps you out.

Edited August 29, 2006 by lilkev715

[martymcfly]

What level math is this?

[lilkev715]

Looks like basic Trig to me.

[CmpFreak88]

Yeah changed all the modes and such, I just had to use approx(cos(3/5)) and that gave me the angle. Oh and this is for Calculus, we're doing our review.

[martymcfly]

Go into "Mode" and change "Exact" to "Approx".

Edited August 29, 2006 by martymcfly

[94Camaro]

Go ahead and enter it just like you were, but instead of pressing enter, press the green diamond key, and then press enter.

 

I find it easier to leave the exact/approx setting on auto and just press that one extra key when I need the approx, cause I need the exact quite a bit as well.

[DECwakeboarder]

Personally I leave mine on exact and then use the diamond key+enter for when I need an approx value...teachers love it when you give them a perfect, exact value every time (until they realize the power of the 89 and make you use a 83 )

[LoArmistead]

I was asked (while taking an upper level calc course) what I thought the single greatest invention by man was. I responded with, "The TI-89." Without that beautifully crafted piece of American ingenuity, I would have jumped out of a third floor window multiple times by now. I always thought the 83 was God's gift to man, but when I discovered the capabilities of the 89, I was in awe.

 

...and yes I believe diamond + enter should convert it to longhand. I remember experiencing that with roots.

[ic3_man]

I was asked (while taking an upper level calc course) what I thought the single greatest invention by man was. I responded with, "The TI-89." Without that beautifully crafted piece of American ingenuity, I would have jumped out of a third floor window multiple times by now. I always thought the 83 was God's gift to man, but when I discovered the capabilities of the 89, I was in awe.

 

...and yes I believe diamond + enter should convert it to longhand. I remember experiencing that with roots.

 

You guys got to use a calculator in class for calc? We never got even touch one at all, everything had to be done using your brain and a pencil...

[hardnrg]

oh come on now... how do you do arccos(3/5) in your head, or even on paper?

 

do you use slide rule? or draw it out and use a protractor?!

 

oh wait... i know... a cosine/sine/tangent lookup table!!!! rofl!!! i've seen those!