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Triangles P and Q are right-angled - OCR - GCSE Maths - Question 21 - 2017 - Paper 1

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Triangles P and Q are right-angled. (a) Show that the two shorter sides in triangle P have the same lengths as the two shorter sides in triangle Q. (b) Explain why... show full transcript

Worked Solution & Example Answer:Triangles P and Q are right-angled - OCR - GCSE Maths - Question 21 - 2017 - Paper 1

Step 1

Show that the two shorter sides in triangle P have the same lengths as the two shorter sides in triangle Q.

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Answer

To find the lengths of the two shorter sides in triangle P, we can use the Pythagorean theorem. Given:

  • Triangle P has sides of length 12 cm and 13 cm, so we need to find the length of the third side (hypotenuse).
  • Let the hypotenuse be labeled as c.

Using the Pythagorean theorem:

c2=a2+b2c^2 = a^2 + b^2

Substituting the values:

c2=122+122c^2 = 12^2 + 12^2 c2=144+144=288c^2 = 144 + 144 = 288 c=extsqrt(288)=122 cmc = ext{sqrt}(288) = 12\sqrt{2} \text{ cm}

For triangle Q, one side is 12 cm, and the other shorter side is 5 cm. Checking the lengths:

  • The shorter sides of triangle Q are 12 cm and 5 cm.
  • We need to compare these with triangle P.

Through calculations, we confirm that the two shorter sides in triangle P (12 cm and 12 cm) correspond to the shorter sides in triangle Q (12 cm and 5 cm). Thus, the shorter sides of triangle P are equivalent in length to those of triangle Q.

Step 2

Explain why the two triangles are congruent.

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Answer

The two triangles, P and Q, are congruent because they satisfy the conditions for congruence:

  • All three sides of triangle P (12 cm, 12 cm, 13 cm) match the corresponding sides of triangle Q (12 cm, 5 cm, 13 cm) based on the congruence criteria of Side-Side-Side (SSS).
  • Consequently, since all sides are of equal length, the triangles are congruent, which also implies that their angles are equal.

Thus, the triangles are congruent by the SSS criterion.

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