যদি cos\(\theta\)+sec\(\theta\)=2 হয়, তবে \(cos^{11}\theta +sec^{11}\theta\)এর মান হবে – (a) 0 (b) 1 (c) 2 (d) 22
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Answer: C
\(cos \theta + sec \theta = 2\)
বা, \(cos \theta + \cfrac{1}{cos \theta} = 2\)
বা, \(\cfrac{cos^2 \theta + 1}{cos \theta} = 2\)
বা, \(cos^2 \theta + 1=2cos \theta\)
বা, \(cos^2 \theta + 1-2cos \theta=0\)
বা, \((cos \theta - 1)^2=0\)
বা, \(cos \theta - 1=0\)
বা, \(cos \theta =1\)
\(cos^{11}\theta+sec^{11}\theta\)
\(cos^{11}\theta+\cfrac{1}{cos^{11}\theta}\)
\(=(1)^{11}+\cfrac{1}{1^{11}}\)
\(=1+1\)
\(=2\)
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