(i) Equilateral triangle

• The number of axes of symmetry is \(3\).
• All the sides are of the same length.
• Every interior angle is \(60^\circ\).

(ii) Isosceles triangle

• The number of axes of symmetry is \(1\).
• Two of the sides have the same length.
• The two base angles are of the same size.

(iii) Scalene triangle

• The number of axes of symmetry is \(0\).
• All the sides are of different lengths.
• All the interior angles are of different sizes.

(iv) Acute-angled triangle

• Every interior angle is an acute angle.

(v) Obtuse-angled triangle

• One of the interior angles is an obtuse angle.

(vi) Right-angled triangle

• One of the interior angles is a right angle (\(90^\circ\)).

• The sum of all the interior angles is \(180^\circ\).
• The sum of an interior angle and its adjacent exterior angle is \(180^\circ\).
• An exterior angle is the sum of two opposite interior angles.