The triangle ABC has an angle A = 30 degrees, and the outer angle at angle B is 40 degrees. Find angle B and angle C.

From the condition it is known that in the triangle ABC, the angle A is 30 °, and the external angle at the angle B is 40 °. In order to find the angle B and the angle C, recall what the sum of adjacent angles and the theorem on the sum of the angles of a triangle are equal to.

So, the sum of adjacent angles is 180 °. Based on this, we can find the angle of triangle B.

180 ° – 40 ° = 140 ° angle of triangle B.

We know the two corners of the triangle.

From the theorem on the sum of the angles of a triangle, we know that the sum of the angles of a triangle is 180 °.

We are looking for angle C:

180 ° – (30 ° + 140 °) = 180 ° – 170 ° = 10 °.