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AP EAMCET · Maths · Trigonometric Equations

If \(\sin \theta+2 \cos \theta=1\) and \(\theta\) belongs to \(4^{\text {th }}\) quadrant (not lying on the coordinate axes) then \(7 \cos \theta+6 \sin \theta=\)

  1. A \(\frac{4}{17}\)
  2. B \(2\)
  3. C \(\frac{7}{17}\)
  4. D \(\frac{4}{5}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(2\)

Step-by-step Solution

Detailed explanation

\( \sin \theta = 1 - 2 \cos \theta \) \( (1 - 2 \cos \theta)^2 + \cos^2 \theta = 1 \) \( 1 - 4 \cos \theta + 4 \cos^2 \theta + \cos^2 \theta = 1 \) \( 5 \cos^2 \theta - 4 \cos \theta = 0 \) \( \cos \theta (5 \cos \theta - 4) = 0 \) \( \cos \theta = \frac{4}{5} \) (since…