TI-89 Titanium: EVALUATING

**tupac** · August 26th 2008, 07:32 PM

I need to get an answer for this
arccos(0.3) on [0, pi)

What do i need to press to get an answer for that?

Thank you.

**mr fantastic** · August 26th 2008, 10:13 PM

Originally Posted by tupac

I need to get an answer for this
arccos(0.3) on [0, pi)

What do i need to press to get an answer for that?

Thank you.

Press mode and make sure you're in radian mode.
Press the green key (diamond), then z, then (, then 0.3, then ), then ENTER.

**tupac** · August 27th 2008, 04:51 PM

Originally Posted by mr fantastic

Press mode and make sure you're in radian mode.
Press the green key (diamond), then z, then (, then 0.3, then ), then ENTER.

What if i have this:
arccos(0.3) on [0, 2pi)

Does it change anything?
And for the first problem do i need to include the [0,pi) anywhere when i input the numbers?
Also what should i press for my calculator to show: arccsc

**mr fantastic** · August 27th 2008, 08:40 PM

Originally Posted by tupac

What if i have this:
arccos(0.3) on [0, 2pi)

Does it change anything?
And for the first problem do i need to include the [0,pi) anywhere when i input the numbers?
Also what should i press for my calculator to show: arccsc

The range of the arcos function is not defined over [0, 2pi).

I'm guessing that your question is actually how to solve $\cos \theta = 0.3$ for $0 \leq \theta < 2 \pi$ . You go to the F2 menu and select 1: solve(

Then it's

solve(cos x = 0.3, x)|0<x<2pi

**tupac** · August 28th 2008, 11:54 AM

Originally Posted by mr fantastic

The range of the arcos function is not defined over [0, 2pi).

I'm guessing that your question is actually how to solve $\cos \theta = 0.3$ for $0 \leq \theta < 2 \pi$ . You go to the F2 menu and select 1: solve(

Then it's

solve(cos x = 0.3, x)|0<x<2pi

what should i press for my calculator to show: arccsc

**mr fantastic** · August 28th 2008, 03:51 PM

Originally Posted by tupac

what should i press for my calculator to show: arccsc

There're no buttons.

It's a nasty surprise for many students when they discover that sometimes you actually have to understand the mathematical concepts before you can press buttons on the CAS calculator and get an answer.

$\text{arccsc} (a) = \theta \Rightarrow \text{csc} \, \theta = a \Rightarrow \frac{1}{\sin \theta} = a \Rightarrow \sin \theta = \frac{1}{a} \Rightarrow \theta = \arcsin \left( \frac{1}{a}\right)$ .

What? It's not April Fools day where you live ......?

Then I guess I better say that I'm joking and that you go to the MATH A:Trig menu and scroll down to what you want ..... Note that $\text{csc}^{-1}$ means the same as arccsc .......

p.s. I wasn't joking about the nasty surprise business ......

p.p.s. Read the TI-89 Titanium manual (download it from the TI website if you did what most other students do and lost it 42 seconds after opening the packaging of your calculator).

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