If the two sides of an isosceles triangle are 2cm and 5cm in length, then its perimeter is______ ．

If the two sides of an isosceles triangle are 2cm and 5cm in length, then its perimeter is______ ．

∵ the length of two sides of isosceles triangle is 2cm and 5cm respectively. According to the triangle trilateral relationship, the waist length of isosceles triangle can not be 2, but can only be 5. The circumference of isosceles triangle = 5 + 5 + 2 = 12cm

If the sides of an isosceles triangle are 2 and 5, its perimeter is a: 7 B: 9 C: 12 d: P or 12

C: Because the sum of two sides in the triangle must be greater than the third side, when 2 is waist, then the two waist 2 + 2 = 4 < 5, and the third side can only be 5 waist, so the perimeter = 5 + 5 + 2 = 12

An isosceles triangle, two sides of which are two fifths and three fourths long, what is the perimeter of this triangle?

1. Perimeter = 2 / 5 × 2 + 3 / 4 = 4 / 5 + 3 / 4 = 31 / 20
2. Perimeter = 3 / 4 × 2 + 2 / 5 = 3 / 2 + 2 / 5 = 19 / 10