If the vertex angle of an isosceles triangle is 120 ° and the length of the contour line at the bottom is 1cm, then its waist length is______ cm

If the vertex angle of an isosceles triangle is 120 ° and the length of the contour line at the bottom is 1cm, then its waist length is______ cm

∵ the top angle of an isosceles triangle is 120 °, the bottom angle of an isosceles triangle is 30 °, and the length of the high line on the bottom edge is 1cm, ∵ its waist length is 2cm

If the vertex angle of an isosceles triangle is 120 ° and the height of its bottom is 3, its perimeter is___ ．

∵ the vertex angle of isosceles triangle is 120 °, the height on the bottom edge is 3, the waist length is 6, the half of the bottom edge is 33, and the circumference is 6 + 6 + 2 × 33 = 12 + 63

If the top angle of isosceles triangle is 120 ° and the height on the bottom is 3cm, the waist length is______ cm．

As shown in the figure, ab = AC, ad ⊥ BC is at the point D, ad = 3cm, ∠ BAC = 120 °, ∫⊥ BAC = 120 °, ab = AC ∫ B = ∠ C = (180 ° - ⊥ BAC) △ 2 = 30 ° ∫ ad ⊥ BC ∫ AB = 3 △ 12 = 6cm