Relationship between Isosceles and Equilateral Triangles
Isosceles and equilateral triangles are both types of triangles with specific properties. Let's explore the relationship between the two sets:

Isosceles Triangles (I)
- An isosceles triangle is a triangle with at least two sides of equal length.
- The two equal sides are called legs, and the third side is called the base.
- The angles opposite the equal sides are also equal in an isosceles triangle.

Equilateral Triangles (E)
- An equilateral triangle is a triangle with all three sides of equal length.
- All three angles in an equilateral triangle are also equal, each measuring 60 degrees.
- An equilateral triangle is a special case of an isosceles triangle where all sides are equal.

Relationship
- Every equilateral triangle is also an isosceles triangle because it has at least two sides of equal length.
- However, not every isosceles triangle is an equilateral triangle, as an isosceles triangle can have only two equal sides, not necessarily all three.
In conclusion, the relationship between isosceles and equilateral triangles is that every equilateral triangle is an isosceles triangle, but not every isosceles triangle is an equilateral triangle.