Triangle ABC and triangle PQR are plotted in the coordinate plane. Find the lengths of AB¯¯¯¯¯¯¯¯ and BC¯¯¯¯¯¯¯¯, then state the length of PQ¯¯¯¯¯¯¯¯ needed to prove that triangle ABC and triangle PQR are congruent by the HL Congruence Theorem.

Coordinates ABC Triangle: A= (1,5) B= (1,2) C= (5,2)
Coordinates PQR Triangle: P=(1-1,-3) Q= (-3-3) R= (-6,-3)

AB=___, BC=___, PQ=____

1 answer

To find the lengths of the sides of triangles ABC and PQR, we can use the distance formula, which is given by:

\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]

Step 1: Calculate length of AB

Points A and B have coordinates A(1, 5) and B(1, 2):

\[ AB = \sqrt{(1 - 1)^2 + (2 - 5)^2} = \sqrt{0 + (-3)^2} = \sqrt{9} = 3 \]

Step 2: Calculate length of BC

Points B and C have coordinates B(1, 2) and C(5, 2):

\[ BC = \sqrt{(5 - 1)^2 + (2 - 2)^2} = \sqrt{(4)^2 + 0} = \sqrt{16} = 4 \]

Step 3: Calculate length of PQ

Points P and Q have coordinates P(-2, -3) and Q(-3, -3):

\[ PQ = \sqrt{(-3 - (-2))^2 + (-3 - (-3))^2} = \sqrt{(-3 + 2)^2 + 0} = \sqrt{(-1)^2} = 1 \]

Final Results:

  • \( AB = 3 \)
  • \( BC = 4 \)
  • \( PQ = 1 \)

Conclusion

To prove that triangles ABC and PQR are congruent by the HL Congruence Theorem, we need to check that the lengths of the hypotenuses are equal. Given that we have found:

  • Length of AB = 3
  • Length of BC = 4

For triangle PQR to be congruent to triangle ABC via the HL theorem, \( PQ \) must equal the hypotenuse of triangle ABC. Since triangle ABC is a right triangle (with right angle at B), we can find the length of AC using the Pythagorean theorem:

\[ AC = \sqrt{AB^2 + BC^2} = \sqrt{3^2 + 4^2} = \sqrt{9 + 16} = \sqrt{25} = 5 \]

Thus, \( PQ \) must equal 5 for the triangles to be congruent.

So, the answers are:

  • \( AB = 3 \)
  • \( BC = 4 \)
  • \( PQ = 5 \) (needed length)