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Mathematics 22 Online
OpenStudy (anonymous):

jl

OpenStudy (ivancsc1996):

First we need to get a picture in our heads:|dw:1375144063850:dw| I arbitrarily chose that the radius of the circle is one.

OpenStudy (ivancsc1996):

\[\csc x=\frac{ 1 }{ \cos x }=9 \rightarrow \cos x=\frac{ 1 }{ 9 }\]So:|dw:1375144288301:dw|Here I think you need to use some Half angle dormulas.

OpenStudy (ivancsc1996):

First half-angle formula: \[\cos x=2 \cos ^{2} \frac{ x }{ 2 }-1 \rightarrow \cos \frac{ x }{ 2 }=\sqrt{\frac{ \cos x +1 }{ 2 }}=\sqrt{\frac{ \frac{ 1 }{ 9 }+1 }{ 2 }}\]Now you do the same with this formulas: \[cosx=1-2 \sin ^{2} \frac{ x }{ 2 }\]For the last one, just divide the sin and the cos

OpenStudy (ivancsc1996):

Well, I had that doubt because you are right. The problem is that the initial condition is cscx=9, not -9

OpenStudy (ivancsc1996):

Well, acording to my equation, cos should be sqrt 10/18

OpenStudy (ivancsc1996):

Oh yeah you are right

OpenStudy (ivancsc1996):

You just need to apply the half.angle formula's I gave for what you got for cosx

OpenStudy (phi):

jhalt post your work for cos x/2 (I assume you already have sin x/2 ?)

OpenStudy (phi):

yes, I understand... but what did you do ?

OpenStudy (phi):

isn't cos x = - sqrt(80)/9 ?

OpenStudy (phi):

yes you are doing 1 + cos(x) as the first step so 1 + - sqrt(80)/9

OpenStudy (phi):

looks good

OpenStudy (phi):

tan is sin / cos

OpenStudy (phi):

yes, that all is correct

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