Definition
In an i.p.s, [ilmath](X,\langle\cdot,\cdot\rangle)[/ilmath] we define [ilmath]x[/ilmath] and [ilmath]y[/ilmath] being perpendicular[1] if:
- [ilmath]\langle x,y\rangle=0[/ilmath]
and we write:
- [ilmath]x\perp y[/ilmath]
References
- ↑ Functional Analysis - George Bachman and Lawrence Narici