√ ( 9 - ( x^2 + y^2 ) ) = c | quadrieren
9 - ( x^2 + y^2 ) = c^2
- ( x^2 + y^2 ) = c^2 - 9 | * -1
x^2 + y^2 = 9 - c^2
y^2 = 9 - c^2 - x^2 | Wurzel
y = ± √ ( 9 - c^2 - x^2 )
2 / ( x + y ) = c
2 = c * ( x + y )
2 / c = x + y
2 / c - x = y
y = 2 / c - x