State in each case whether A ⊂ B or A ⊄ B. A = {x : x is a triangle in a plane}, B = {x : x is a rectangle in the same plane}

Question

Philoid · Accepted Answer

A ⊄ B

We have, A = set of triangles and B = set of rectangles.

Now, we can see elements of A does not belong to B since the set of rectangles does not include a set of triangles.