Answer:
π/2 (90°)
Step-by-step explanation:
The dot product of two vectors equals the product of their magnitudes and the cosine of the angle between them.
a·b = ||a|| ||b|| cos θ
If the dot product is 0:
0 = ||a|| ||b|| cos θ
0 = cos θ
θ = π/2
The angle between a and b is π/2 (90°).