Supplementary Angle Identities: Analyzing Trigonometry Beyond \(90^\circ\)

Supplementary Angle Identities: Analyzing Trigonometry Beyond \(90^\circ\)

Secondary 3

In the diagram, \(ABC\) is a right-angled triangle in which \(\angle BAC=90{}^\circ \).
\(AC=16\) cm, \(BC=20\) cm, \(AB\) is produced to \(P\) and \(AC\) is produced to \(Q\).

  1. Calculate \(\angle ABC\), correct to \(1\) decimal place.
  2. Express each of the following as a fraction, in its simplest form.
    1. \(\sin \angle BCA\),
    2. \(\cos \angle BCQ\).

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Answer:(a) \(53.1^\circ\) (b)(i) \(\frac{3}{5}\) (ii) \(-\frac{4}{5}\)

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