A right angle is exactly 90°. An obtuse angle is greater than 90° and less than 180°, a straight line. An isosceles triangle with all angles less than 90° is an acute-angled triangle.

It categorizes triangles into equilateral, isosceles, scalene, obtuse, right, and acute based on their sides and angles. The video also covers the concept of congruency, demonstrating how two ...