Find the limit n → ∞ lim ( sin n x + cos n x ) n 1 at x = 3 π .
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In fact n → ∞ lim ( a n + b n ) n 1 = m a x ( a , b )
Nice question+solution..+1 .
L = n → ∞ lim ( sin n x + cos n x ) n 1 = n → ∞ lim sin x ( 1 + cot n x ) n 1 = n → ∞ lim 2 3 ( 1 + ( 3 1 ) n ) n 1 = 2 3 ( 1 + 0 ) 0 = 2 3 At x = 3 π
You can plug in x = 3 π straight away and from that it is pretty simple. But is plugging in straight away always correct (can it be deceitful) ?
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bring out ( s i n x ) n from the expression therefore we get
lim n → ∞ s i n x ( 1 + ( c o t x ) n ) n 1
= [ ( lim n → ∞ s i n x ]*[ lim n → ∞ ( 1 + ( c o t x ) n ) n 1 ]
As c o t ( π / 3 ) is less than 1 therefore lim n → ∞ ( 1 + ( c o t x ) n ) n 1 =1
therefore answer is s i n ( π / 3 ) = 3 / 2