Answer:
The triangle is obtuse.
Step-by-step explanation:
If a² + b² < c² , the triangle is obtuse.
If a² + b² = c² , the triangle is right triangle.
If a² + b² > c² , the triangle is acute.
~~~~~~~~~~~~~~~~
3, 12, 13
3² + 12² < 13²
9 + 144 < 169
153 < 169 ⇒ the triangle is obtuse.
