JEE Mains · Maths · STD 11 - 3. trignometrical ratios,functions and identities
The value of \({\cos ^2}\,{10^o}\,\, - \,\cos \,\,{10^o}\,\cos \,\,{50^o}\, + \,{\cos ^2}\,{50^o}\) is
- A \(\frac{3}{2}\,(1\, + \,\cos \,{20^o})\)
- B \(\frac {3}{4}\)
- C \(\frac {3}{2}\)
- D \(\frac{3}{4}\,\, + \,\,\cos \,{20^o}\)
Answer & Solution
Correct Answer
(B) \(\frac {3}{4}\)
Step-by-step Solution
Detailed explanation
\(\frac{1}{2}\,(2\,{\cos ^2}{10^o}\, - \,2\cos \,{10^o}\,\cos \,{50^o} + \,2\,{\cos ^2}{50^o})\) \( \Rightarrow \frac{1}{2}\,(1 + \,\cos \,{20^o} - (\cos \,{60^o} + \cos \,{40^o})\, + 1 + \,\,\cos {100^o})\)…
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