Question

Let $U$ be the set of all triangles in a plane. If $A$ is the set of all triangles with atleast one angle different from $60^{\circ }$, then $A^{\prime }$ is the

• A. set of right angled triangle
• B. set of equilateral triangle
• C. set of isosceles triangle
• D. None of the above

Answer 1

Answer: (B)

$A=$ Set of all triangles atleast one angle different from $60^{\circ }$.
$A^{\prime }=$ Set of all triangles with all angles is of $60^{\circ }$.