Acute-Angled Triangle:
a<90°, b<90°, c<90°
(all 3 angles of a triangle are between 0° & 90°)
Right-Angled Triangle:
a=90° or b=90° or c=90°
(any 1 angle of a triangle is 90°)
Obtuse-Angled Triangle:
a>90° or b>90° or c>90°
(any 1 angle of a triangle is between 90° & 180°)