In an isosceles triangle, the outer apex angle is 40 degrees. Find the angles of this triangle.

According to the triangle external angle theorem, the value of any external angle of a triangle is equal to the sum of two other angles of this triangle, not adjacent to the given external angle. Since, according to the condition of the problem, the outer angle at the apex of this isosceles triangle is 40 degrees, the sum of the two angles at the base of the triangle is also 40 degrees. The angles at the base of an isosceles triangle are equal, therefore each of them is equal to 40/2 = 20 degrees.
The sum of the angles of any triangle is 180 degrees, which means that the angle at the apex is 180-20-20 = 140 degrees.
Therefore, the desired angles of a given triangle are 140, 20 and 20 degrees.