In the diagram, ∠ PSR = 220°, ∠ SPQ = 58° and ∠ PQR =

MATHEMATICS
WAEC 2010

In the diagram, ∠ PSR = 220°, ∠ SPQ = 58° and ∠ PQR = 41°. Calculate the obtuse angle QRS.

  • A. 90°
  • B. 100°
  • C. 121°
  • D. 60°

Correct Answer: C. 121°

Explanation

Joining SQ. In \(\bigtriangleup\) SPQ,

(22o + a) + 55o + (41o + b) = 180o

121o + a + b = 180o

a + b = 180 - 121

a + b = 59o.....(1)

In \(\bigtriangleup\) SRPQ; R + a + b = 180o

R + 59o = 180o

(in (1), a + b = 59o)

R = 180 - 59

R = 121o



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