Which of the following statements is true. Why?

Which of the following statements is true. Why?(a) Every equilateral triangle is an isosceles triangle.(b) Every isosceles triangle is an equilateral triangle.

(a) It is true In an equilateral triangle, all three sides are equal. It can be an isosceles triangle also, which has two sides equal. (b) But every isosceles triangle need not be an equilateral triangle.