In vector scalar product, why a ⊥ B a * b = 0

In vector scalar product, why a ⊥ B a * b = 0

A ⊥ B the angle between a and B = 90 & # 186; = π / 2
∴ a*b=│a││b│cosπ/2=0
This is my conclusion after meditation,
If not, please ask, I will try my best to help you solve it~
If you are not satisfied, please understand~