The population in a statistical study is determined by all the individuals that could be part of the study, that is, all the individuals that have common characteristics that make them individuals of interest to the researcher.
In the study of the previous statement, the population is made up of all recruits from the US Army. UU. in Iraq at the time of the study.
A composition is operation between function that consist in replacing the independent variable of the first function, in this case, for . Common notations for composition between functions are and . If we know that and , then .
So basically you need to use the pythagorean thrm. Essentially, the diagonal and the width and length create a triangle, the diagonal being the hypothenuse. So the formula goes as . the variable "a" being the length and the variable "b" being the width. So plug it in and there you have your answer!