Proofs in Plane Geometry - Similarity

Proofs in Plane Geometry - Similarity

IP 2
5 marks

In the diagram, triangles \(ABC\) and \(ADE\) are similar, such that \(AE = 10\text{ cm}\), \(AD = 8\text{ cm}\), \(DE = 6\text{ cm}\), \(BC = 10\text{ cm}\) and angle \(EAD = 37^\circ\).

Precision clarification: the \(6\)-\(8\)-\(10\) triangle has \(\angle EAD\approx36.87^\circ\). The printed \(37^\circ\) is interpreted as rounded to the nearest degree.

  1. Show that triangle \(ADE\) is a right-angled triangle.

    [2]
  2. Calculate angle \(ACB\).

    [1]
  3. Calculate \(BE\), giving your answer to \(1\) decimal place.

    [2]

Solution:

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Answer:(a) Right-angled at \(D\). (b) Approximately \(53^\circ\) (nearest degree). (c) \(BE=3.3\text{ cm}\) (1 d.p.).

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