Question

Classify following triangle into acute, obtuse, right triangle:
In $△ABC,\angle A={10}^o,\angle B={70}^o,\angle C={100}^o$.

Answer 1

In the given triangle, one angle is greater than $90°(\angle C>90°)⟹$obtuse angle

and two angles are less than $90°\left(\angle A\text{and}\angle B\right)$. Hence the given triangle is obtuse triangle.