Ascertain

To render (a person) certain; to cause to feel certain; to make confident; to assure; to apprise.

To make (a thing) certain to the mind; to free from obscurity, doubt, or change; to make sure of; to fix; to determine.

To find out or learn for a certainty, by trial, examination, or experiment; to get to know; as, to ascertain the weight of a commodity, or the purity of a metal.

establish after a calculation, investigation, experiment, survey, or study; "find the product of two numbers"; "The physicist who found the elusive particle won the Nobel Prize"