These acute angles are the same. It does not matter how long the lines are because it is the amount of turn that is being measured. Image caption, An obtuse angle is between 90° and 180°.

An isosceles triangle with angles of 50°, 50° and 80° is an acute-angled triangle. Image caption, A scalene triangle with all angles less than 90° is an acute-angled triangle. A scalene ...