Solve, by factorising, the equation
\(6 \cos \theta \tan \theta - 3 \cos \theta + 4 \tan \theta - 2 = 0,\)
for \(0^\circ \leq \theta \leq 180^\circ\).
Solution
Start with the equation:
\(6 \cos \theta \tan \theta - 3 \cos \theta + 4 \tan \theta - 2 = 0\)
Factorise by grouping:
\(3 \cos \theta (2 \tan \theta - 1) + 2 (2 \tan \theta - 1) = 0\)
Factor out \((2 \tan \theta - 1)\):
\((2 \tan \theta - 1)(3 \cos \theta + 2) = 0\)
Set each factor to zero:
\(2 \tan \theta - 1 = 0\) or \(3 \cos \theta + 2 = 0\)
Solve for \(\theta\):
\(\tan \theta = \frac{1}{2}\)
\(\theta = \tan^{-1}\left(\frac{1}{2}\right) \approx 26.6^\circ\)
\(\cos \theta = -\frac{2}{3}\)
\(\theta = \cos^{-1}\left(-\frac{2}{3}\right) \approx 131.8^\circ\)
Thus, the solutions are \(\theta = 26.6^\circ\) and \(\theta = 131.8^\circ\).
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