関連ワード:  equilateral triangle formula class 9    isosceles triangle formula class 9    equilateral triangle area formula class 9    isosceles triangle area formula class 9    perimeter of equilateral triangle formula class 9    isosceles triangle height formula class 9    height of equilateral triangle formula class 9    isosceles triangle perimeter formula class 9    isosceles triangle heron's formula class 9    altitude of equilateral triangle formula class 9