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-   -   Trig Identity Problem (http://www.physicsforums.com/showthread.php?t=93169)

Briggs Oct9-05 01:23 PM

Trig Identity Problem
 
I have been set an exercise from my text book to do for homework but I am having some problems on one of the questions, I havn't encountered any of this type before and I am quite stumped.

"Eliminate [tex]\theta[/tex] from equations [tex]x=2+\csc\theta[/tex] and [tex]y=\frac{1}{4}\tan\theta[/tex]"

So I am guessing I start off with x=y but then... :confused:

Fermat Oct9-05 02:56 PM

start off by getting separate expressions for cscθ and tanθ from each of your two eqns.
Now you have to eliminate θ.
Can you do it from there ?

Briggs Oct9-05 03:02 PM

So for the first one would it goto,
[tex]2+\frac{1}{\sin\theta}=3+\cot\theta[/tex] Then try eliminate theta from there?

Fermat Oct9-05 03:31 PM

not quite.
get two separate expressions. One for cscθ and one for tanθ.
Then find a trig identity involving the trig functions. You will have to manipulate the functions to get the identity.

Briggs Oct9-05 04:42 PM

I'm not sure what you are saying, get an expression for each equation so for the first one would become [tex]2+\cot\theta[/tex] and the second one [tex]\frac{1}{4}\csc\theta-\frac{1}{4}[/tex] then put them equal to each other and try solve it?
I would appreciate it if you could show me the first step in tex form

Fermat Oct9-05 04:47 PM

hang on a minute.

Fermat Oct9-05 04:51 PM

x = 2 + cscθ
y = ╝tanθ

cscθ = x - 2
tanθ = 4y

1 + tan▓θ = sec▓θ

Briggs Oct9-05 04:57 PM

Ahhh, it all becomes clear. Thanks a lot for the help It seems so easy now.


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