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Then <br> | Then <br> | ||
<math> | <math> | ||
\mathbf{v}^T \mathbf{K} \mathbf{v}= \mathbf{v}^T [\sum_j K_{ij}v_j] | |||
\mathbf{v}^T \mathbf{K} \mathbf{v} | = \sum_i \sum_j v_{i}K_{ij}v_{j} | ||
= \sum_i \sum_j v_{i}\phi(\mathbf{x}^{(i)})^T\phi(\mathbf{x}^{(j)})v_{j} | |||
= \sum_i \sum_j v_{i} \sum_k \phi_k(\mathbf{x}^{(i)}) \phi_k(\mathbf{x}^{(j)})v_{j} | |||
= \sum_k \sum_i \sum_j v_{i} \phi_k(\mathbf{x}^{(i)}) \phi_k(\mathbf{x}^{(j)})v_{j} | |||
= \sum_k \sum_i v_{i} \phi_k(\mathbf{x}^{(i)}) \sum_j \phi_k(\mathbf{x}^{(j)})v_{j} | |||
= \sum_k (\sum_i v_{i} \phi_k(\mathbf{x}^{(i)}))^2 | |||
\geq 0 | |||
</math> | </math> | ||
}} | }} |