In triangle ABC, angle A = 80 degrees, angle B = 20 degrees, angle C = 80 degrees, what kind of triangle ABC?

Let us find out what is the angle A of the indicated triangles, if we know from the conditions that it is equal to 80 °:

80 <90 (this is an acute angle).

Let us find out what is the angle B of the indicated triangles, if we know from the conditions that it is equal to 20 °:

20 <90 (acute angle).

Let us find out what is the angle C of the indicated triangles, if we know from the conditions that it is equal to 80 °:

80 <90 (acute angle).

Answer: Since after comparisons it is known that all the corners of this triangle are acute, then the indicated triangle is acute-angled.