Se da la ecuación de superficie de 2 grado:
− 2 2 x z − 2 6 x + z 2 − 2 3 z − 1 = 0 - 2 \sqrt{2} x z - 2 \sqrt{6} x + z^{2} - 2 \sqrt{3} z - 1 = 0 − 2 2 x z − 2 6 x + z 2 − 2 3 z − 1 = 0 Esta ecuación tiene la forma:
a 11 x 2 + 2 a 12 x y + 2 a 13 x z + 2 a 14 x + a 22 y 2 + 2 a 23 y z + 2 a 24 y + a 33 z 2 + 2 a 34 z + a 44 = 0 a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x z + 2 a_{14} x + a_{22} y^{2} + 2 a_{23} y z + 2 a_{24} y + a_{33} z^{2} + 2 a_{34} z + a_{44} = 0 a 11 x 2 + 2 a 12 x y + 2 a 13 x z + 2 a 14 x + a 22 y 2 + 2 a 23 yz + 2 a 24 y + a 33 z 2 + 2 a 34 z + a 44 = 0 donde
a 11 = 0 a_{11} = 0 a 11 = 0 a 12 = 0 a_{12} = 0 a 12 = 0 a 13 = − 2 a_{13} = - \sqrt{2} a 13 = − 2 a 14 = − 6 a_{14} = - \sqrt{6} a 14 = − 6 a 22 = 0 a_{22} = 0 a 22 = 0 a 23 = 0 a_{23} = 0 a 23 = 0 a 24 = 0 a_{24} = 0 a 24 = 0 a 33 = 1 a_{33} = 1 a 33 = 1 a 34 = − 3 a_{34} = - \sqrt{3} a 34 = − 3 a 44 = − 1 a_{44} = -1 a 44 = − 1 Las invariantes de esta ecuación al transformar las coordenadas son los determinantes:
I 1 = a 11 + a 22 + a 33 I_{1} = a_{11} + a_{22} + a_{33} I 1 = a 11 + a 22 + a 33 |a11 a12| |a22 a23| |a11 a13|
I2 = | | + | | + | |
|a12 a22| |a23 a33| |a13 a33| I 3 = ∣ a 11 a 12 a 13 a 12 a 22 a 23 a 13 a 23 a 33 ∣ I_{3} = \left|\begin{matrix}a_{11} & a_{12} & a_{13}\\a_{12} & a_{22} & a_{23}\\a_{13} & a_{23} & a_{33}\end{matrix}\right| I 3 = a 11 a 12 a 13 a 12 a 22 a 23 a 13 a 23 a 33 I 4 = ∣ a 11 a 12 a 13 a 14 a 12 a 22 a 23 a 24 a 13 a 23 a 33 a 34 a 14 a 24 a 34 a 44 ∣ I_{4} = \left|\begin{matrix}a_{11} & a_{12} & a_{13} & a_{14}\\a_{12} & a_{22} & a_{23} & a_{24}\\a_{13} & a_{23} & a_{33} & a_{34}\\a_{14} & a_{24} & a_{34} & a_{44}\end{matrix}\right| I 4 = a 11 a 12 a 13 a 14 a 12 a 22 a 23 a 24 a 13 a 23 a 33 a 34 a 14 a 24 a 34 a 44 I ( λ ) = ∣ a 11 − λ a 12 a 13 a 12 a 22 − λ a 23 a 13 a 23 a 33 − λ ∣ I{\left(\lambda \right)} = \left|\begin{matrix}a_{11} - \lambda & a_{12} & a_{13}\\a_{12} & a_{22} - \lambda & a_{23}\\a_{13} & a_{23} & a_{33} - \lambda\end{matrix}\right| I ( λ ) = a 11 − λ a 12 a 13 a 12 a 22 − λ a 23 a 13 a 23 a 33 − λ |a11 a14| |a22 a24| |a33 a34|
K2 = | | + | | + | |
|a14 a44| |a24 a44| |a34 a44| |a11 a12 a14| |a22 a23 a24| |a11 a13 a14|
| | | | | |
K3 = |a12 a22 a24| + |a23 a33 a34| + |a13 a33 a34|
| | | | | |
|a14 a24 a44| |a24 a34 a44| |a14 a34 a44| sustituimos coeficientes
I 1 = 1 I_{1} = 1 I 1 = 1 | ___|
|0 0| |0 0| | 0 -\/ 2 |
I2 = | | + | | + | |
|0 0| |0 1| | ___ |
|-\/ 2 1 | I 3 = ∣ 0 0 − 2 0 0 0 − 2 0 1 ∣ I_{3} = \left|\begin{matrix}0 & 0 & - \sqrt{2}\\0 & 0 & 0\\- \sqrt{2} & 0 & 1\end{matrix}\right| I 3 = 0 0 − 2 0 0 0 − 2 0 1 I 4 = ∣ 0 0 − 2 − 6 0 0 0 0 − 2 0 1 − 3 − 6 0 − 3 − 1 ∣ I_{4} = \left|\begin{matrix}0 & 0 & - \sqrt{2} & - \sqrt{6}\\0 & 0 & 0 & 0\\- \sqrt{2} & 0 & 1 & - \sqrt{3}\\- \sqrt{6} & 0 & - \sqrt{3} & -1\end{matrix}\right| I 4 = 0 0 − 2 − 6 0 0 0 0 − 2 0 1 − 3 − 6 0 − 3 − 1 I ( λ ) = ∣ − λ 0 − 2 0 − λ 0 − 2 0 1 − λ ∣ I{\left(\lambda \right)} = \left|\begin{matrix}- \lambda & 0 & - \sqrt{2}\\0 & - \lambda & 0\\- \sqrt{2} & 0 & 1 - \lambda\end{matrix}\right| I ( λ ) = − λ 0 − 2 0 − λ 0 − 2 0 1 − λ | ___| | ___|
| 0 -\/ 6 | |0 0 | | 1 -\/ 3 |
K2 = | | + | | + | |
| ___ | |0 -1| | ___ |
|-\/ 6 -1 | |-\/ 3 -1 | | ___ ___|
| ___| |0 0 0 | | 0 -\/ 2 -\/ 6 |
| 0 0 -\/ 6 | | | | |
| | | ___| | ___ ___|
K3 = | 0 0 0 | + |0 1 -\/ 3 | + |-\/ 2 1 -\/ 3 |
| | | | | |
| ___ | | ___ | | ___ ___ |
|-\/ 6 0 -1 | |0 -\/ 3 -1 | |-\/ 6 -\/ 3 -1 |
I 1 = 1 I_{1} = 1 I 1 = 1 I 2 = − 2 I_{2} = -2 I 2 = − 2 I 3 = 0 I_{3} = 0 I 3 = 0 I 4 = 0 I_{4} = 0 I 4 = 0 I ( λ ) = − λ 3 + λ 2 + 2 λ I{\left(\lambda \right)} = - \lambda^{3} + \lambda^{2} + 2 \lambda I ( λ ) = − λ 3 + λ 2 + 2 λ K 2 = − 10 K_{2} = -10 K 2 = − 10 K 3 = − 16 K_{3} = -16 K 3 = − 16 Como
I 3 = 0 ∧ I 4 = 0 ∧ I 2 ≠ 0 I_{3} = 0 \wedge I_{4} = 0 \wedge I_{2} \neq 0 I 3 = 0 ∧ I 4 = 0 ∧ I 2 = 0 entonces por razón de tipos de rectas:
hay que
Formulamos la ecuación característica para nuestra superficie:
− I 1 λ 2 + I 2 λ − I 3 + λ 3 = 0 - I_{1} \lambda^{2} + I_{2} \lambda - I_{3} + \lambda^{3} = 0 − I 1 λ 2 + I 2 λ − I 3 + λ 3 = 0 o
λ 3 − λ 2 − 2 λ = 0 \lambda^{3} - \lambda^{2} - 2 \lambda = 0 λ 3 − λ 2 − 2 λ = 0 λ 1 = 2 \lambda_{1} = 2 λ 1 = 2 λ 2 = − 1 \lambda_{2} = -1 λ 2 = − 1 λ 3 = 0 \lambda_{3} = 0 λ 3 = 0 entonces la forma canónica de la ecuación será
( x ~ 2 λ 1 + y ~ 2 λ 2 ) + K 3 I 2 = 0 \left(\tilde x^{2} \lambda_{1} + \tilde y^{2} \lambda_{2}\right) + \frac{K_{3}}{I_{2}} = 0 ( x ~ 2 λ 1 + y ~ 2 λ 2 ) + I 2 K 3 = 0 2 x ~ 2 − y ~ 2 + 8 = 0 2 \tilde x^{2} - \tilde y^{2} + 8 = 0 2 x ~ 2 − y ~ 2 + 8 = 0 x ~ 2 4 − y ~ 2 8 = − 1 \frac{\tilde x^{2}}{4} - \frac{\tilde y^{2}}{8} = -1 4 x ~ 2 − 8 y ~ 2 = − 1 es la ecuación para el tipo cilindro hiperbólico
- está reducida a la forma canónica