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(1/2)*ln(2*y+1)=C-ln(cos(x)) equation

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Numerical solution:

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The solution

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log(2*y + 1)                  
------------ = c - log(cos(x))
     2                        
$$\frac{\log{\left(2 y + 1 \right)}}{2} = c - \log{\left(\cos{\left(x \right)} \right)}$$
Detail solution
Given the equation
$$\frac{\log{\left(2 y + 1 \right)}}{2} = c - \log{\left(\cos{\left(x \right)} \right)}$$
$$\frac{\log{\left(2 y + 1 \right)}}{2} = c - \log{\left(\cos{\left(x \right)} \right)}$$
Let's divide both parts of the equation by the multiplier of log =1/2
$$\log{\left(2 y + 1 \right)} = 2 c - 2 \log{\left(\cos{\left(x \right)} \right)}$$
This equation is of the form:
log(v)=p

By definition log
v=e^p

then
           c - log(cos(x))
           ---------------
                 1/2      
2*y + 1 = e               

simplify
$$2 y + 1 = \frac{e^{2 c}}{\cos^{2}{\left(x \right)}}$$
$$2 y = \frac{e^{2 c}}{\cos^{2}{\left(x \right)}} - 1$$
$$y = \frac{e^{2 c}}{2 \cos^{2}{\left(x \right)}} - \frac{1}{2}$$
The graph
Sum and product of roots [src]
sum
        /   2*c \       /   2*c \
        |  e    |       |  e    |
      re|-------|   I*im|-------|
        |   2   |       |   2   |
  1     \cos (x)/       \cos (x)/
- - + ----------- + -------------
  2        2              2      
$$\frac{\operatorname{re}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} + \frac{i \operatorname{im}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} - \frac{1}{2}$$
=
        /   2*c \       /   2*c \
        |  e    |       |  e    |
      re|-------|   I*im|-------|
        |   2   |       |   2   |
  1     \cos (x)/       \cos (x)/
- - + ----------- + -------------
  2        2              2      
$$\frac{\operatorname{re}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} + \frac{i \operatorname{im}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} - \frac{1}{2}$$
product
        /   2*c \       /   2*c \
        |  e    |       |  e    |
      re|-------|   I*im|-------|
        |   2   |       |   2   |
  1     \cos (x)/       \cos (x)/
- - + ----------- + -------------
  2        2              2      
$$\frac{\operatorname{re}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} + \frac{i \operatorname{im}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} - \frac{1}{2}$$
=
        /   2*c \       /   2*c \
        |  e    |       |  e    |
      re|-------|   I*im|-------|
        |   2   |       |   2   |
  1     \cos (x)/       \cos (x)/
- - + ----------- + -------------
  2        2              2      
$$\frac{\operatorname{re}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} + \frac{i \operatorname{im}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} - \frac{1}{2}$$
-1/2 + re(exp(2*c)/cos(x)^2)/2 + i*im(exp(2*c)/cos(x)^2)/2
Rapid solution [src]
             /   2*c \       /   2*c \
             |  e    |       |  e    |
           re|-------|   I*im|-------|
             |   2   |       |   2   |
       1     \cos (x)/       \cos (x)/
y1 = - - + ----------- + -------------
       2        2              2      
$$y_{1} = \frac{\operatorname{re}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} + \frac{i \operatorname{im}{\left(\frac{e^{2 c}}{\cos^{2}{\left(x \right)}}\right)}}{2} - \frac{1}{2}$$
y1 = re(exp(2*c)/cos(x)^2)/2 + i*im(exp(2*c)/cos(x)^2)/2 - 1/2