Right equilateral is not an appropriate classification for a triangle.
Explanation:
Option a: Right equilateral
It is not possible for an equilateral triangle to be right. Because in an equilateral triangle all three angles are equal. But, in a right angled triangle not all three angles are equal.
Thus, right equilateral is not an appropriate classification for a triangle.
Option b: Acute scalene
In a scalene triangle, all three sides have different lengths. In a acute scalene triangle all three angles are acute.
Thus, Acute scalene is an appropriate classification for a triangle.
Option c: Obtuse isosceles
An isosceles triangle has two equal sides. In a obtuse isosceles triangle which has an angle more than 90° but less than 180°.
Thus, Obtuse isosceles is an appropriate classification for a triangle.
Option d: Right scalene
A scalene triangle is a triangle which has three unequal sides. A right angled triangle is a scalene triangle since it has three unequal sides.
Thus, Right isosceles is an appropriate classification for a triangle.
Hence, Right equilateral is not an appropriate classification for a triangle.
