(a) Using a ruler and a pair of compasses only, construct (i) a triangle XYZ in which /YZ/ = 8cm, < XYZ = 60° and < XZY = 75°. Measure /XY/; (ii) the locus ...

Assessment: WAEC SSCE - General Mathematics - 1994 (Essay) Subject: General Mathematics

Question 1 Report

(a) Using a ruler and a pair of compasses only, construct (i) a triangle XYZ in which /YZ/ = 8cm, < XYZ = 60° and < XZY = 75°. Measure /XY/; (ii) the locus \(l_{1}\) of points equidistant from Y and Z ; (iii) the locus \(l_{2}\) of points equidistant from XY and YZ.

(b) Measure QY where Q is the point of intersection of \(l_{1}\) and \(l_{2}\).

Answer Details

(a)(i) Construction of triangle \(XYZ\)

  1. Draw \(YZ=8\text{ cm}\).
  2. At \(Y\), construct an angle of \(60^\circ\). At \(Z\), construct an angle of \(75^\circ\), using ruler and compasses only.
  3. Let the two constructed rays meet at \(X\). This gives triangle \(XYZ\).
figure
Completed ruler-and-compass construction. The dashed line \(l_1\) is the perpendicular bisector of \(YZ\); the dashed ray \(l_2\) is the internal angle bisector at \(Y\).

From the completed construction,

\[|XY|\approx 10.9\text{ cm}.\]

(a)(ii) The locus \(l_1\) of points equidistant from \(Y\) and \(Z\) is the perpendicular bisector of \(YZ\).

(a)(iii) The locus \(l_2\) of points equidistant from \(XY\) and \(YZ\) is the internal bisector of \(\angle XYZ\).

(b) Let \(Q\) be the intersection of \(l_1\) and \(l_2\). Measuring from the construction gives

\[\boxed{|QY|\approx 4.8\text{ cm}}\]

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