the arccos of pie: is this negative one, or undefined?

[MINYgenius]

is the arccos of pie

negative one?

or undefined?

 

[mmm4444bot]

Re: need help now plzzz! trig.



If you understand the definition of the arccosine function and you know its domain, then the answer to this exercise is easy.

Did your class skip over the definitions of the inverse trigonometric functions?

Do you have any specific questions about the terminology in this exercise?

Do you know what the term "domain" means, with respect to functions?

We do not, in general, provide lessons at this site.

CLICK HERE FOR BASIC LESSON ON THE ARCCOS FUNCTION.

If, after reading this lesson, you still have questions, then please come back here and tell us why you're stuck, so that we know how to help you further.

Cheers,

~ Mark

PS: The correct spelling of the constant is "Pi". (Pie are round, but Pi*r^2.)

 

[fasteddie65]

Your question may be backwards. Usually arccos involves a number other than ?. (pi, not pie, BTW)

arccos ? is undefined because the domain of arccos is [-1,1].

cos ? = -1 but that's not what you asked.

Maybe you should look at the question again and resubmit it.

 

[mmm4444bot]

... arccos ? is undefined ...

... Maybe you should look at the question again ...

Hey Fast Eddie:

Since arccos(?) is undefined, why is "undefined" not the answer to this exercise?

~ Mark :?

 

[pka]

Hey Fast Eddie:
Since arccos(?) is undefined, why is "undefined" not the answer to this exercise?

Fast Eddie is correct this time!
\(\displaystyle \pi\) is not in the domain of the arccosine function.

 

[mmm4444bot]

... Fast Eddie is correct this time!

He usually is, quite boiled-down, cut-to-the-bone, in a nutshell.

Since the exercise is multiple choice -- and one of the choices is "undefined" -- I do not understand why Fast Eddie provides the correct choice followed by a suggestion to the original poster to reread the exercise.

I might be misinterpreting PKA's comment. Heck, I might be misinterpreting the exercise.

~ Mark :?

 

[Deleted member 4993]

Since

\(\displaystyle |\cos(\theta)| \le 1\)

\(\displaystyle \cos^{-1}(\pi)\) does not exist in real domain.

 

[mmm4444bot]

... does not exist ...

This is why I believe that the correct choice is "undefined".

Are you also trying to suggest that the original poster's exercise is invalid?

 

[Deleted member 4993]

Yes - because the function cannot even approach that "domain" (way way beyond 1)

 

[mmm4444bot]

Yes ...

I categorize this exercise as a trick question, not an invalid question.

I claim that a fundamental knowledge of the arccos function is sufficient to enable the original poster to correctly choose the second answer.

~ Mark