I am confused about the definition of the inner product
-is it : [tex]P:\mathbb{R}^n\times \mathbb{R}^n\rightarrow \mathbb{R}[/tex]
-or: [tex]P:\mathbb{R}^n\times \mathbb{R}^n\rightarrow \mathbb{R} ^+[/tex]
I know that it's [tex]\mathbb{R} ^+[/tex] from my teacher
why it's [tex]\mathbb{R} ^+[/tex] ?
An inner product which is also a dot product is negative sometimes if the angle is between pi/2 and 3pi/2