ABC is an isosceles triangle. Angle C = 70 degrees Find the sides of an isosceles triangle.

In the formulation of the task, the question remained open: what angle C is what angle? One that is equal to another angle (then, naturally, the third angle will be equal to 180 ° – 2 * 70 ° = 40 °) or one that is not equal to other equal angles (in this case, two angles will have a degree measure, equal to (180 ° – 70 °): 2 = 55 °.
It should be noted that in the setting of the task, without setting any parameter of the triangle, which is expressed by the distance between two points (side, height, median, and so on), it is required to find the sides of an isosceles triangle. As you know, a triangle is uniquely (that is, up to equality) reconstructed, basically, according to the following triples of basic elements: two sides and the angle between them (for example, sides a, b and the angle between them C); side and two corners (for example, side a and corners B and C); all three sides (a, b and c). Note that one cannot take any triple of basic elements in the equality criteria, even if one of them is a side, for example, a triangle cannot be uniquely constructed from the elements a, b and angle B.
So, it is not possible to fulfill the requirement of this task due to the lack of sufficient information.