The triangle PQR above is

  • A an obtuse-angled triangle
  • B a scalene triangle
  • C an isosceles triangle
  • D an equilateral triangle
jamb 2002mathematics

The correct answer is C. an isosceles triangle

∠PQR = 180 - 128 (∠s on a straight line)

= 52

∠QPR + 76 + 52 = 180(extr ∠ = sum of intr. opp ∠s)

∠QPR + 128 = 180

∠QPR = 180 - 128

= 52

∴ΔPQR is an isosceles triangle

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