It is known that the circumference of an isosceles triangle is 20 cm. One side is 5 cm. What are the other sides?

It is known that the circumference of an isosceles triangle is 20 cm. One side is 5 cm. What are the other sides?

When it is a waist, because it is an isosceles triangle, so the other two sides are waist 5 and bottom 20-5-5 = 10. But according to the sum of any two sides of the triangle is greater than the third side, and 5 + 5 = 10, so it can't. when 5 is the bottom, the other two waist are (20-5) / 2 = 7.5 and 7.5