Solve : \(\tan (2x - 15)° - 1 = 0\), for values of x such that \(0° \leq x \leq 360°\).

Assessment: WAEC SSCE - Further Mathematics - 2015 (Essay) Subject: Further Mathematics

Question 1 Report

Solve : \(\tan (2x - 15)° - 1 = 0\), for values of x such that \(0° \leq x \leq 360°\).

Answer Details

Solve \(\tan(2x-15)^{\circ}-1=0\) for \(0^{\circ}\le x\le 360^{\circ}\).

\[\tan(2x-15)^{\circ}=1\]

The tangent is \(1\) at \(45^{\circ}\) and every \(180^{\circ}\) thereafter, so

\[2x-15=45+180n\quad(n\in\mathbb{Z})\]\[2x=60+180n\;\Rightarrow\;x=30+90n\]

Take values of \(x\) in \([0^{\circ},360^{\circ}]\):

  • \(n=0:\ x=30^{\circ}\)
  • \(n=1:\ x=120^{\circ}\)
  • \(n=2:\ x=210^{\circ}\)
  • \(n=3:\ x=300^{\circ}\)

Hence \(x=30^{\circ},\ 120^{\circ},\ 210^{\circ},\ 300^{\circ}\).

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