where do people use Pascal triangle?

Answer 1

It helps when you want to determine constants in expressions like
(a+b)^2(or any other power).

Another words, if you know that such expressions are based on Pascal triangle, you can use this fact when factoring, simplifying, or solving binomials, polynomials, and like.

Answer 2

It's really useful for the binomial theorem when raising something to any power.

Answer 3

in binomial theorem