## if the cos inverse of x=pie/3 what is the sin inverse of x ?

Trigonometric ratios and functions, the unit circle, inverse trig functions, identities, trig graphs, etc.

### if the cos inverse of x=pie/3 what is the sin inverse of x ?

if the cos inverse of x= pie/3 what is the sin inverse of x ?

Posts: 79
Joined: Sun Feb 22, 2009 11:12 pm

theshadow wrote:if the cos inverse of x= pie/3 what is the sin inverse of x ?

I'm going to guess that you don't mean $\frac{\pi e}{3}$, but just $\frac{\pi}{3}$. (The Greek letter used to represent the geometrical value approximated by 3.14159 is spelled "pi"; a "pie" is a baked dessert.)

Use the definition of inverse trig functions: If cos-1(x) = (pi)/3, then cos[(pi)/3] = x. This is what the inverse-cosine function is and does.

Remembering the reference-angle values you've memorized, what is the value of cos((pi)/3)? So what is the value of "x"?

You now need to find sin-1(x). Plug in the value you found for x, and work backwards to the answer, using those same reference-angle values.

If you get stuck, please reply showing how far you have gotten. Thank you!

stapel_eliz

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Joined: Mon Dec 08, 2008 4:22 pm

### Re: if the cos inverse of x=pie/3 what is the sin inverse of x ?

cos((pi)/3) = 1/2, so i'm just taking sin inverse of 1/2?

Posts: 79
Joined: Sun Feb 22, 2009 11:12 pm

theshadow wrote:cos((pi)/3) = 1/2, so i'm just taking sin inverse of 1/2?

Yup!

stapel_eliz

Posts: 1803
Joined: Mon Dec 08, 2008 4:22 pm

### Re: if the cos inverse of x=pie/3 what is the sin inverse of x ?

A great strategy to deal with these problems is to list all the values along the unit circle like this: http://www.math.ucsd.edu/~jarmel/math4c/Unit_Circle_Angles.png. That way when you have to deal with arc trig problems you have an easy refrence to look up the answers.
richards

Posts: 1
Joined: Fri Apr 10, 2009 7:27 pm