I know that D ⃗ v f = ∇ f ⋅ ⃗ v Dv→f=∇f⋅v→ is the directional derivative. My question is why must the vector ⃗ v v→ be a unit vector? I am sure there is an obvious answer, but my book doesn't really explain it.
closed as off-topic by Marcus Müller, MBaz, Peter K.♦ Mar 31 '17 at 14:34
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "This question does not appear to be about signal processing within the scope defined in the help center." – Marcus Müller, MBaz, Peter K.