# Simplify With Assumptions Not Using Distributive Property Of Dot Product

Given the following expression

Assuming[(n | d | t) ∈ Vectors[3, Reals] && n.t == 0, FullSimplify[(n + d).t]]


Why does mathematica give me the below instead of simplifying to d.t?

(d + n).t


You can add TensorExpand to achieve this:
Assuming[(n | d | t) ∈ Vectors[3, Reals] && n.t == 0,

As I understand it, manipulating symbolic tensors should generally be done with the Tensor* family of functions (guide page). This is not built-in in functions like FullSimplify .