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JEE Mains · Maths · STD 11 - 3. trignometrical ratios,functions and identities

If \(0 <  x , y < \pi\) and \(\cos x +\cos y-\cos ( x + y )=\frac{3}{2},\) then \(\sin x+\cos y\) is equal to ...... .

  1. A \(\frac{1}{2}\)
  2. B \(\frac{1+\sqrt{3}}{2}\)
  3. C \(\frac{\sqrt{3}}{2}\)
  4. D \(\frac{1-\sqrt{3}}{2}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1+\sqrt{3}}{2}\)

Step-by-step Solution

Detailed explanation

\(\cos x+\cos y-\cos (x+y)=\frac{3}{2}\) \(\cos ^{2}\left(\frac{x+y}{2}\right)-\cos \left(\frac{x+y}{2}\right) \cdot \cos \left(\frac{x-y}{2}\right)\) \(+\frac{1}{4} \cdot \cos ^{2}\left(\frac{x-y}{2}\right)+\frac{1}{4} \sin ^{2}\left(\frac{x-y}{2}\right)=0\)…
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