The statistical mean can also be used to interpret statistical data. Some important properties make statistical mean very useful for measuring central tendency. Since Xi - X is the distance from a given number to the average. The numbers to the left of the mean are balanced by the numbers to the right of the mean.
In review, vertical angles are angles formed by the intersection of two lines while alternate interior angles, alternate exterior angles, corresponding angles and consecutive interior angles are formed by the intersection of two lines and a transversal.
You are right - an equilateral triangle cannot have an obtuse angle. In fact, the angles are all fixed - they are each 60 degrees. Try this: take three equal length pencils and form a triangle. Now take three more pencils and try to form a triangle that has angles different from the first.