An isosceles triangle has 2 of the same sides so there are two possible answers:
1) 26° is one of the angles which is the same as another. 26° × 2 = 52° and since there are 180° in a triangle the other angle is 180° - 52° which is 128°. This would make the angles 26°, 26° and 128°
2) 26° is not one of the angles which is the same as another. Since there are 180° in a triangle, the other angles would both be 2 ÷ (180° - 26°) which is 77°. This would make the angless 26°, 77° and 77°
