f
(
x
,
y
) =
x
²/2 +
y
²/2
u
= ⟨cos
φ
, sin
φ
⟩ at
P
0
(1, 1)
D
u
f = 1.41
A: u points along ∇f
D
u
f
= ∇
f
·
u
=
1.41
of
‖∇
f
‖
=
1.41
Snap to:
A: fastest increase
B: fastest decrease
C: no change
▶ Play
φ =
45
°