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