हिंदी

Show that the relation R, defined in the set A of all polygons as R = {(P1, P2) : P1 and P2 have the same number of sides}, is an equivalence relation.

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प्रश्न

Show that the relation R, defined in the set A of all polygons as R = {(P1, P2) : P1 and P2 have the same number of sides}, is an equivalence relation. What is the set of all elements in A related to the right-angled triangle T with sides 3, 4 and 5?

योग
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उत्तर

We observe the following properties on R:

Reflexivit:

Let P1 be an arbitrary element of A.

Then, polygon P1 and P1 have the same number of sides, since they are one and the same.

⇒ (P1, P1) ∈ R for all P1 ∈ A

So, R is reflexive on A.

Symmetry:

Let (P1, P2) ∈ R

⇒ P1 and P2 have the same number of sides.

⇒ P2 and P1 have the same number of sides.

⇒ (P2, P1) ∈ R for all P1, P2 ∈ A 

So, R is symmetric on A.

Transitivity:

Let (P1, P2), (P2, P3) ∈ R

⇒ P1 and P2 have the same number of sides and P2 and P3 have the same number of sides.

⇒ P1, P2 and P3 have the same number of sides.

⇒ P1 and P3 have the same number of sides.

⇒ (P1, P3) ∈ R for all P1, P3 ∈ A

So, R is transitive on A.

Hence, R is an equivalence relation on the set A.

Also, the set of all the triangles ∈ A is related to the right angle triangle T with the sides 3, 4, and 5.

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अध्याय 1: Relations - Exercise 1.2 [पृष्ठ २७]

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आर.डी. शर्मा Mathematics Volume 1 and 2 [English] Class 12
अध्याय 1 Relations
Exercise 1.2 | Q 10 | पृष्ठ २७

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