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 ...

Properties of symmetry: - Students may notice symmetry in the isosceles and equilateral triangles and non-symmetry in the scalene triangles Informal recognition of these properties may be helpful in ...