Question

A regular polygon with three sides is,
(a) an isosceles triangle
(b) a scalene triangle
(c) an equilateral triangle
(d) an obtuse-angled triangle

Answer 1

Hint: In order to solve this problem, we need to know the definition of all the terms in the question as well as in the answers. The regular polygon is a 2-dimensional shape with all sides to be equal. The isosceles triangle is a shape of 3 sides from which only 2 sides are equal. An equilateral triangle is a shape of 3 sides from which all the 3 sides are equal. A scalene triangle is a triangle with all the sides to be different.

Complete step-by-step answer:
The polygon with three sides is called a triangle.
The word triangle explains itself, “tri-angle” means three angles.
Three types of triangles distinguish on the basis on the relation between the sides of the triangle are as below,
(i) equilateral triangle (ii) isosceles triangle (iii) scalene triangle.
The equilateral triangle is the triangle with all the three sides equal.
It can be shown as below,

We can see that in the triangle CDE, CD = DE = CE.
The isosceles triangle is the triangle with only two sides equal.
It can be shown as below,

We can see that in triangle FGH, $\text{FG = FH}\ne \text{GH}$ .
The scalene triangle is the triangle with all the side are different.
It can be shown as below,

We can see that in triangle IJK, all three sides are of different length.
Let us understand the definition of the regular polygon.
The polygon with all the sides equal is called a regular polygon. In our question, it is asked about the regular polygon with three sides.
Therefore, the regular polygon with three sides is an equilateral triangle.
Hence, the correct option is (c).
Note: As we can see that in option (d) says that an obtuse angle triangle. So, there is no relation in the length of the sides of the triangle. Therefore, we can eliminate the option (d). By the definitions of regular polygon, equilateral, isosceles and scalene triangle we can figure out the correct option.