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Friday, July 26, 2013

Proving - Congruent Triangles, 2

Category: Plane Geometry

"Published in Newark, California, USA"

In the given figure, if MR PN; NR MP, prove that ∆NOR
∆MOP.

Photo by Math Principles in Everyday Life

Solution:

 Consider the given figure above

Photo by Math Principles in Everyday Life

Proof:

1. Statement: MR PN and NR MP.

    Reason: Given items.

2. Statement: PR PR

    Reason: Reflexive property of congruence.

3. Statement: ∆MRP ∆NPR

    Reason: Side Side Side (SSS) Postulate.

4. Statement: ∠MPR ≅ NRP
                      ∠PMR ≅ ∠PNR
                      ∠PRM ≅ RPN

    Reason: Since ∆MRP ≅ NPR, then all interior angles of a triangle are congruent to all interior angles of other triangle. 

5. Statement: ∠PRM ≅ 4 and ∠RPN ≅ 3.

    Reason: Reflexive property of congruence.

6. Statement: ∠PRM ≅ RPN ≅ 3 ≅ 4

    Reason: Transitive property of congruence.

7. Statement: ∆POR is an isosceles triangle.

    Reason: The two angles of an isosceles triangle are congruent. Hence, 3 ≅ 4 at the base.

8. Statement: OP OR

    Reason: Since ∆POR is an isosceles triangle, then the two sides of an isosceles triangle are congruent.

9. Statement: MPR = 1 + 3 and NRP = 2 + ∠4

    Reason: Addition property of angles.

10. Statement: ∠1 ≅ ∠2

      Reason: If MPR ≅ NRP and 3 ≅ 4, then it follows that 1 ≅ 2.

11. Statement: ∆MOP ∆NOR 

      Reason: Side Angle Side (SAS) Postulate.