Answer:
Obtuse triangle
Explanation:
Given the side lengths :
3, 9, 10
Let :
a = 3 ; b = 9 ; c = 10 (longest side)
If a² + b² = c² (right angle)
If a² + b² > c² (acute angle)
If a² + b² < c² (obtuse angle)
a² + b²
3² + 9²
9 + 81 = 90
c² = 10² = 100
90 < 100
Hence,
a² + b² < c² (then we have an obtuse triangle)