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If cos x = - \(\frac{5}{13}\) where 180° < X < 270°, what is the...

Mathematics
NECO 2001

If cos x = - \(\frac{5}{13}\) where 180° < X < 270°, what is the value of tan x -sin x ?

  • A. \(\frac{111}{13}\)
  • B. \(\frac{321}{65}\)
  • C. \(\frac{216}{65}\)
  • D. \(\frac{112}{13}\)
  • E. \(\frac{131}{65}\)
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Correct Answer: Option C
Explanation

Given \(\cos x = -\frac{5}{13}\) where \(180^\circ < x < 270^\circ\):

Using: \(\sin^2 x + \cos^2 x = 1\)

\(\sin^2 x = 1 - \left(-\frac{5}{13}\right)^2 = \frac{144}{169} \implies \sin x = -\frac{12}{13}\)

\(\tan x = \frac{\sin x}{\cos x} = \frac{-\frac{12}{13}}{-\frac{5}{13}} = \frac{12}{5}\)

Calculating \(\tan x - \sin x\):

\(\tan x - \sin x = \frac{12}{5} - \left(-\frac{12}{13}\right) = \frac{12}{5} + \frac{12}{13}\)

Finding a common denominator (65):

\(\tan x - \sin x = \frac{12 \times 13}{65} + \frac{12 \times 5}{65} = \frac{156}{65} + \frac{60}{65} = \frac{216}{65}\)

Thus, the value is:

\(\tan x - \sin x = \frac{216}{65}\)


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