Let U be the set of all triangles in a plane. If A is the set of all triangles with at least one angle different from 60°, what is
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friends plzzz explain me this....
Given : A is the set of all triangles with at least one angle different from 60°
⇒ A' is the set of all triangles with all angles 60°
Hence, A' is the set of all equilateral triangles.