For fabric at least 10 cm wider than half the chest measurement, 2 lengths + 1 sleeve length + 100 cm. For fabric at least 10 cm wider than 1/4 chest measurement: 4 lengths + 1 sleeve length + 200 cm. These are rough estimates and should give you plenty of fabric for a basic shirt or blouse. Add more for gathering, design features like bias cuts, pleats, etc.
An isosceles triangle is a triangle with two congruent sides and congruent base angles. congruent means equal. No matter which direction the triangle's apex, or peak, points, it's an isosceles triangle if two of its sides are congruent.
The altitude drawn on the base of an isosceles triangle helps in finding the area of the triangle, which is half the product of the altitude and the base. If all three sides and angles of a triangle are equal, it is called an equilateral triangle. Thus, an equilateral triangle is also an isosceles triangle.