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TS EAMCET · Maths · Trigonometric Equations

If \(5 \cos x+12 \cos y=13\), then the maximum value of \(5 \sin x+12 \sin y\) is :

  1. A 12
  2. B \(\sqrt{120}\)
  3. C \(\sqrt{20}\)
  4. D 13
Verified Solution

Answer & Solution

Correct Answer

(B) \(\sqrt{120}\)

Step-by-step Solution

Detailed explanation

\(\because 5 \cos x+12 \cos y=13\) \(\Rightarrow \quad(5 \cos x+12 \cos y)^2=169\) \(\therefore(5 \cos x+12 \cos y)^2+(5 \sin x+12 \sin y)^2\) \(\Rightarrow \quad(13)^2+(5 \sin x+12 \sin y)^2\) \(=25+144+120(\sin x \sin y+\cos x \cos y)\)…