content_image/301075.jpg content_image/301076.jpg content_image/301080.jpg
<img src='content_image/301075.jpg'>

<img src='content_image/301076.jpg'>

Then { v$_{1}$ , w$_{1}$ , ..., w$_{ℓ}$$_{−}$$_{2}$ , v$_{2}$ } is an orthogonal basis for R $^{ℓ}$, and φ$_{π}$ is given by 

<img src='content_image/301080.jpg'>

