In triangle ABC, angle A = 41º, angle C = 91º. Find the outside angle at vertex B.

Since the sum of the angles of any triangle is 180º, the angle B in triangle ABC is 180º – 41º – 91º = 48º.

The outer angle at vertex B is equal to the adjacent angle for B, that is, 180º – 48º = 132º.

Answer: The adjacent vertex angle B of triangle ABC is 132º.

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