The angles of an isosceles triangle are 2: 5: 5. Find the angle between the lateral strings.

Enter the proportionality coefficient x and the angles of the triangle are equal: 2x, 5x, 5x. The sum of the angles of the triangle is 180 °, we get the following equation:
2x + 5x + 5x = 180
12x = 180
x = 15
2 * 15 = 30 °;
5 * 15 = 75 °;
5 * 15 = 75 °.
Two equal angles are the angles at the base of an isosceles triangle.
The smaller angle is the apex angle or the angle between the sides.
Answer: the degree measure of the angle between the sides is 30 °.