reflexive property of congruence
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A topology is a set of elements or subsets that follows these properties:∅ and X belongs to the setAny union of the subsets belongs to the set.Any intersection of the subsets belongs to the set.Yes, any intersection of two topologies on X is always a topology on X. Consider this example:Let X = {1,2,3}, T = {∅, {1},{2},{1,2},X} and S = {∅, {1}, {3}, {1,3},X}Then, S ∩ T = {∅, X, {1}}To show that S ∩ T is a topology, we need to prove these properties:∅ and X belongs to the setAny union of the subsets belongs to the set.Any intersection of the subsets belongs to the set.Step 1: Prove the first property is followedSince the empty set and X belongs to S ∩ T, the first property is followed. That is obvious. ;)Step 2: Prove the second property is followedSelect any union of any pair of subsets. You should see that this property is also satisfied. How?∅ U X = X ∈ S ∩ T∅ U {1} = {1} ∈ S ∩ T{1} U X = X ∈ S ∩ TStep 3: Prove the third property is followedAny intersection of the subsets belong to the set obviously. See below:∅ ∩ X = ∅ ∈ S ∩ T∅ ∩ {1} = ∅ ∈ S ∩ T{1} ∩ X = {1} ∈ S ∩ TSo the intersection of two topologies on X is a topology.
congruent
Identity property of multiplication
You would use the Property Of Zero
p --> q and q --> p are not equivalent p --> q and q --> (not)p are equivalent The truth table shows this. pq p --> q q -->(not)p f f t t f t t t t f f f t t t t