Question

Which of thre following statements are CORRECT ?

• A. All equilateral triangles are isosceles triangles.
• B. All isosceles triangles are equilateral triangles.
• C. Triangles having all their sides and angles as equal in measure are known as equilateral triangles.
• D. Triangles having any two of their angles or any of their two sides are equal are known as isosceles triangles.

Answer 1

Answer: (A), (C), (D)

Triangles having any two of their angles or any of their two sides are equal are known as isosceles triangles.

All the triangles having all the three sides and angles are equal are known as Equilateral triangles.Here, $△ABC$ is an equilateral triangle.

And, all those triangles having two of their sides and angles as equal are known as isosceles triangles.
Here, $△DEF$ is an isosceles triangle having equal side $DE\&EF$ and equal angle $\angle DEF=\angle DFE$

$\to$ As equilateral triangles also have two sides equal so we can say all equilateral triangles are isosceles triangles.


So, statements $\left(a\right)$, $\left(c\right)$ and $\left(d\right)$ are correct.