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x^2+y^2=1 equation

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Numerical solution:

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The solution

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 2    2    
x  + y  = 1
$$x^{2} + y^{2} = 1$$
Detail solution
Move right part of the equation to
left part with negative sign.

The equation is transformed from
$$x^{2} + y^{2} = 1$$
to
$$\left(x^{2} + y^{2}\right) - 1 = 0$$
This equation is of the form
a*x^2 + b*x + c = 0

A quadratic equation can be solved
using the discriminant.
The roots of the quadratic equation:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where D = b^2 - 4*a*c - it is the discriminant.
Because
$$a = 1$$
$$b = 0$$
$$c = y^{2} - 1$$
, then
D = b^2 - 4 * a * c = 

(0)^2 - 4 * (1) * (-1 + y^2) = 4 - 4*y^2

The equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)

x2 = (-b - sqrt(D)) / (2*a)

or
$$x_{1} = \frac{\sqrt{4 - 4 y^{2}}}{2}$$
$$x_{2} = - \frac{\sqrt{4 - 4 y^{2}}}{2}$$
Vieta's Theorem
it is reduced quadratic equation
$$p x + q + x^{2} = 0$$
where
$$p = \frac{b}{a}$$
$$p = 0$$
$$q = \frac{c}{a}$$
$$q = y^{2} - 1$$
Vieta Formulas
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = 0$$
$$x_{1} x_{2} = y^{2} - 1$$
The graph
Rapid solution [src]
           __________________________________________                                                         __________________________________________                                                
          /                      2                       /     /                      2        2   \\        /                      2                       /     /                      2        2   \\
       4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|
x1 = - \/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *cos|------------------------------------------| - I*\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *sin|------------------------------------------|
                                                         \                    2                     /                                                       \                    2                     /
$$x_{1} = - i \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)} - \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)}$$
         __________________________________________                                                         __________________________________________                                                
        /                      2                       /     /                      2        2   \\        /                      2                       /     /                      2        2   \\
     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|
x2 = \/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *cos|------------------------------------------| + I*\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *sin|------------------------------------------|
                                                       \                    2                     /                                                       \                    2                     /
$$x_{2} = i \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)} + \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)}$$
x2 = i*((-re(y)^2 + im(y)^2 + 1)^2 + 4*re(y)^2*im(y)^2)^(1/4)*sin(atan2(-2*re(y)*im(y, -re(y)^2 + im(y)^2 + 1)/2) + ((-re(y)^2 + im(y)^2 + 1)^2 + 4*re(y)^2*im(y)^2)^(1/4)*cos(atan2(-2*re(y)*im(y), -re(y)^2 + im(y)^2 + 1)/2))
Sum and product of roots [src]
sum
      __________________________________________                                                         __________________________________________                                                       __________________________________________                                                         __________________________________________                                                
     /                      2                       /     /                      2        2   \\        /                      2                       /     /                      2        2   \\      /                      2                       /     /                      2        2   \\        /                      2                       /     /                      2        2   \\
  4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|   4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|
- \/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *cos|------------------------------------------| - I*\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *sin|------------------------------------------| + \/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *cos|------------------------------------------| + I*\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *sin|------------------------------------------|
                                                    \                    2                     /                                                       \                    2                     /                                                     \                    2                     /                                                       \                    2                     /
$$\left(- i \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)} - \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)}\right) + \left(i \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)} + \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)}\right)$$
=
0
$$0$$
product
/      __________________________________________                                                         __________________________________________                                                \ /    __________________________________________                                                         __________________________________________                                                \
|     /                      2                       /     /                      2        2   \\        /                      2                       /     /                      2        2   \\| |   /                      2                       /     /                      2        2   \\        /                      2                       /     /                      2        2   \\|
|  4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|| |4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/|     4 /  /      2        2   \        2      2        |atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/||
|- \/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *cos|------------------------------------------| - I*\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *sin|------------------------------------------||*|\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *cos|------------------------------------------| + I*\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *sin|------------------------------------------||
\                                                    \                    2                     /                                                       \                    2                     // \                                                  \                    2                     /                                                       \                    2                     //
$$\left(- i \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)} - \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)}\right) \left(i \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)} + \sqrt[4]{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}{2} \right)}\right)$$
=
     __________________________________________                                              
    /                      2                            /                      2        2   \
   /  /      2        2   \        2      2      I*atan2\-2*im(y)*re(y), 1 + im (y) - re (y)/
-\/   \1 + im (y) - re (y)/  + 4*im (y)*re (y) *e                                            
$$- \sqrt{\left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1\right)^{2} + 4 \left(\operatorname{re}{\left(y\right)}\right)^{2} \left(\operatorname{im}{\left(y\right)}\right)^{2}} e^{i \operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 1 \right)}}$$
-sqrt((1 + im(y)^2 - re(y)^2)^2 + 4*im(y)^2*re(y)^2)*exp(i*atan2(-2*im(y)*re(y), 1 + im(y)^2 - re(y)^2))