The angle at the base of an isosceles triangle is 80 degrees. Find the angle at the vertex 2

Let us determine how many degrees the sum of two angles at the base of this triangle will correspond to, when in this case we know, in accordance with the available data in the condition of our task, that one angle at the base is 80 °:

80 + 80 = 160.

Let us determine how many degrees the remaining angle of this triangle will correspond, when we reliably know from the current school course that the sum of the angles of any triangle is 180 °:

180 – 160 = 20.

Answer: 20 °.