Solving for $z$ in $x=frac y{2 tan(z/2)}$











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I'm trying to solve for $z$ given $x=dfrac y{2 tan(z/2)}$.



Wolfram Alpha gives me the solution, but when I plug the formula into Excel it's not giving expected results at all - if I plug the same $x$ value into the formula it does not give me the $z$ that I originally started with.



Hopefully that's enough information to go off of; normally I frequent Stackoverflow. Thanks!










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  • You should not necessarily be surprised to get back a different value of $z$. Instead you should keep an open mind to the possibility that the equation is satisfied by many choices for $z$ even without changing $x$ and $y$. A formula that Excel can use will only produce a single value.
    – Jyrki Lahtonen
    yesterday















up vote
0
down vote

favorite
1












I'm trying to solve for $z$ given $x=dfrac y{2 tan(z/2)}$.



Wolfram Alpha gives me the solution, but when I plug the formula into Excel it's not giving expected results at all - if I plug the same $x$ value into the formula it does not give me the $z$ that I originally started with.



Hopefully that's enough information to go off of; normally I frequent Stackoverflow. Thanks!










share|cite|improve this question









New contributor




user3763099 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.




















  • You should not necessarily be surprised to get back a different value of $z$. Instead you should keep an open mind to the possibility that the equation is satisfied by many choices for $z$ even without changing $x$ and $y$. A formula that Excel can use will only produce a single value.
    – Jyrki Lahtonen
    yesterday













up vote
0
down vote

favorite
1









up vote
0
down vote

favorite
1






1





I'm trying to solve for $z$ given $x=dfrac y{2 tan(z/2)}$.



Wolfram Alpha gives me the solution, but when I plug the formula into Excel it's not giving expected results at all - if I plug the same $x$ value into the formula it does not give me the $z$ that I originally started with.



Hopefully that's enough information to go off of; normally I frequent Stackoverflow. Thanks!










share|cite|improve this question









New contributor




user3763099 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











I'm trying to solve for $z$ given $x=dfrac y{2 tan(z/2)}$.



Wolfram Alpha gives me the solution, but when I plug the formula into Excel it's not giving expected results at all - if I plug the same $x$ value into the formula it does not give me the $z$ that I originally started with.



Hopefully that's enough information to go off of; normally I frequent Stackoverflow. Thanks!







trigonometry






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edited 2 days ago









amWhy

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asked 2 days ago









user3763099

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user3763099 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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user3763099 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












  • You should not necessarily be surprised to get back a different value of $z$. Instead you should keep an open mind to the possibility that the equation is satisfied by many choices for $z$ even without changing $x$ and $y$. A formula that Excel can use will only produce a single value.
    – Jyrki Lahtonen
    yesterday


















  • You should not necessarily be surprised to get back a different value of $z$. Instead you should keep an open mind to the possibility that the equation is satisfied by many choices for $z$ even without changing $x$ and $y$. A formula that Excel can use will only produce a single value.
    – Jyrki Lahtonen
    yesterday
















You should not necessarily be surprised to get back a different value of $z$. Instead you should keep an open mind to the possibility that the equation is satisfied by many choices for $z$ even without changing $x$ and $y$. A formula that Excel can use will only produce a single value.
– Jyrki Lahtonen
yesterday




You should not necessarily be surprised to get back a different value of $z$. Instead you should keep an open mind to the possibility that the equation is satisfied by many choices for $z$ even without changing $x$ and $y$. A formula that Excel can use will only produce a single value.
– Jyrki Lahtonen
yesterday










2 Answers
2






active

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up vote
1
down vote













We have



$$x=frac y {2 tan(z/2)} iff tan(z/2)=frac y {2x} iff z=2arctan frac y {2x}+2kpi$$



provided that $zneq 0 quad xneq 0$.






share|cite|improve this answer





















  • Where does 'k' come from, how do I find this value?
    – user3763099
    2 days ago










  • @user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
    – gimusi
    2 days ago




















up vote
0
down vote













The solution is



$$2 left(pi c_1+cot ^{-1}left(frac{2 x}{y}right)right)$$



where $c_1$ is an integer.



Doesn't this work for you?






share|cite|improve this answer





















  • That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
    – user3763099
    2 days ago












  • $c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
    – KM101
    2 days ago













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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
1
down vote













We have



$$x=frac y {2 tan(z/2)} iff tan(z/2)=frac y {2x} iff z=2arctan frac y {2x}+2kpi$$



provided that $zneq 0 quad xneq 0$.






share|cite|improve this answer





















  • Where does 'k' come from, how do I find this value?
    – user3763099
    2 days ago










  • @user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
    – gimusi
    2 days ago

















up vote
1
down vote













We have



$$x=frac y {2 tan(z/2)} iff tan(z/2)=frac y {2x} iff z=2arctan frac y {2x}+2kpi$$



provided that $zneq 0 quad xneq 0$.






share|cite|improve this answer





















  • Where does 'k' come from, how do I find this value?
    – user3763099
    2 days ago










  • @user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
    – gimusi
    2 days ago















up vote
1
down vote










up vote
1
down vote









We have



$$x=frac y {2 tan(z/2)} iff tan(z/2)=frac y {2x} iff z=2arctan frac y {2x}+2kpi$$



provided that $zneq 0 quad xneq 0$.






share|cite|improve this answer












We have



$$x=frac y {2 tan(z/2)} iff tan(z/2)=frac y {2x} iff z=2arctan frac y {2x}+2kpi$$



provided that $zneq 0 quad xneq 0$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered 2 days ago









gimusi

89.1k74495




89.1k74495












  • Where does 'k' come from, how do I find this value?
    – user3763099
    2 days ago










  • @user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
    – gimusi
    2 days ago




















  • Where does 'k' come from, how do I find this value?
    – user3763099
    2 days ago










  • @user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
    – gimusi
    2 days ago


















Where does 'k' come from, how do I find this value?
– user3763099
2 days ago




Where does 'k' come from, how do I find this value?
– user3763099
2 days ago












@user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
– gimusi
2 days ago






@user3763099 For example $tan x = 1 implies x=arctan (1)+kpi =pi/4+kpi quad kin mathbb{Z}$
– gimusi
2 days ago












up vote
0
down vote













The solution is



$$2 left(pi c_1+cot ^{-1}left(frac{2 x}{y}right)right)$$



where $c_1$ is an integer.



Doesn't this work for you?






share|cite|improve this answer





















  • That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
    – user3763099
    2 days ago












  • $c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
    – KM101
    2 days ago

















up vote
0
down vote













The solution is



$$2 left(pi c_1+cot ^{-1}left(frac{2 x}{y}right)right)$$



where $c_1$ is an integer.



Doesn't this work for you?






share|cite|improve this answer





















  • That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
    – user3763099
    2 days ago












  • $c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
    – KM101
    2 days ago















up vote
0
down vote










up vote
0
down vote









The solution is



$$2 left(pi c_1+cot ^{-1}left(frac{2 x}{y}right)right)$$



where $c_1$ is an integer.



Doesn't this work for you?






share|cite|improve this answer












The solution is



$$2 left(pi c_1+cot ^{-1}left(frac{2 x}{y}right)right)$$



where $c_1$ is an integer.



Doesn't this work for you?







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered 2 days ago









David G. Stork

9,28521232




9,28521232












  • That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
    – user3763099
    2 days ago












  • $c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
    – KM101
    2 days ago




















  • That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
    – user3763099
    2 days ago












  • $c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
    – KM101
    2 days ago


















That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
– user3763099
2 days ago






That's the formula I'm using, but maybe I'm lost as to what integer c1 is supposed to be. To me, this seems like an unsolved value, so I'm frankly confused as to what I should plug in there. Where does this come from?
– user3763099
2 days ago














$c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
– KM101
2 days ago






$c_1$ is any integer value. You probably know that trig functions are periodic. $tan b(x)$ is periodic and repeats every $frac{pi}{b}$ radians. (Every $pi$ radians if $b = 1$.) For example, $tan frac{pi}{4} = tan frac{5pi}{4}$.
– KM101
2 days ago












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