document.write( "Question 1208976: limit (((ln 2))^(x))/(cos ((pi)/4 sin (3 x))) as x \[LongRightArrow] - \[Infinity] = 0 ( T or F ) \n" ); document.write( "
Algebra.Com's Answer #847548 by ikleyn(52776)\"\" \"About 
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\n" ); document.write( "limit (((ln 2))^(x))/(cos ((pi)/4 sin (3 x))) as x \[LongRightArrow] - \[Infinity] = 0 ( T or F )
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document.write( "I placed (copy-pasted) the given expression into the Math editor, and this Math editor interpreted the expression this way\r\n" );
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document.write( "    \"%28%28%28ln+2%29%29%5E%28x%29%29%2F%28cos+%28%28pi%29%2F4+sin+%283+x%29%29%29\".\r\n" );
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document.write( "It is what I will use in my following analysis.\r\n" );
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document.write( "             Step 1.\r\n" );
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document.write( "Consider a sequence of real numbers  \"x%5B1%5D\", \"x%5B2%5D\", \"x%5B3%5D\", . . . , \"x%5Bn%5D\", . . . which approaches to  \"pi%2F18\"  from the left.\r\n" );
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document.write( "Then the sequence of real numbers  \"3%2Ax%5B1%5D\", \"3%2Ax%5B2%5D\", \"3%2Ax%5B3%5D\", . . . , \"3%2Ax%5Bn%5D\", . . . approaches to  \"pi%2F6\"  from the left.\r\n" );
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document.write( "Then the sequence of real numbers  \"sin%283%2Ax%5B1%5D%29\", \"sin%283%2Ax%5B2%5D%29\", \"sin%283%2Ax%5B3%5D%29\", . . . , \"sin%283x%5Bn%5D%29\"  approaches to  \"sin%28pi%2F6%29\" = 1/2  from the left.\r\n" );
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document.write( "Then the sequence of real numbers  \"pi%2F%284%2Asin%283%2Ax%5B1%5D%29%29\", \"pi%2F%284%2Asin%283%2Ax%5B2%5D%29%29\", \"pi%2F%284%2Asin%283%2Ax%5B3%5D%29%29\", . . . , \"pi%2F%284%2Asin%283%2Ax%5Bn%5D%29%29\", . . .  \r\n" );
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document.write( "         approaches to  \"pi%2F%284%2Asin%28pi%2F6%29%29\" = \"pi%2F%284%2A%281%2F2%29%29\" = \"pi%2F2\"  from the left.\r\n" );
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document.write( "Then the sequence of numbers  \"cos%28pi%2F%284%2Asin%283x%5Bk%5D%29%29%29\"  approaches to  0 (zero)  from the right.\r\n" );
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document.write( "Thus for this sequence of numbers  \"x%5Bk%5D\",  the numerator approaches to (ln(2))^(pi/18), which is some constant,\r\n" );
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document.write( "while the denominator  \"cos%28pi%2F%284%2Asin%283x%29%29%29\"  approaches to zero.\r\n" );
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document.write( "Hence, as the argument x approaches to  \"pi%2F18\"  from the left,  \r\n" );
document.write( "the values of the given expression go to positive infinity.\r\n" );
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document.write( "After that, as the argument x becomes greater than \"pi%2F18\", the expression takes finite values, again.\r\n" );
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document.write( "             Step 2.\r\n" );
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document.write( "The function  \"cos%28pi%2F%284%2Asin%283x%29%29%29\"  in the denominator is periodical with the period \"2pi%2F3\".\r\n" );
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document.write( "It means that the behavior of the given expression, which we detected in part (a), repeats inside each period [\"n%2A%282pi%2F3%29\",\"%28n%2B1%29%2A%282pi%2F3%29\"],\r\n" );
document.write( "for all positive or negative integer numbers \"n\".\r\n" );
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document.write( "In other words, inside each such period, there is a converging sequence of real numbers, \r\n" );
document.write( "for which our expression goes to positive infinity, and after that the expression takes finite values, again.\r\n" );
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document.write( "             Step 3.\r\n" );
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document.write( "It means that as x goes to plus or minus infinity, the given expression HAS NO limit.\r\n" );
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document.write( "ANSWER.  Of the two possible options, T or F, only F is valid.\r\n" );
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\n" ); document.write( "\n" ); document.write( "It can be solved in other way, too.\r
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document.write( "In my solution above, I considered a sequence of numbers  \"x%5Bk%5D\",  converging to  pi/6  from the left,\r\n" );
document.write( "and shoved that for such sequence  of arguments the whole function has positive values (going to + infinity).\r\n" );
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document.write( "Similarly, if we consider another sequence of numbers  \"x%5Bk%5D\", converging to pi/6 from the right,\r\n" );
document.write( "we will get the sequence of the values of the whole function, which all are negative and go to - infinity.\r\n" );
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document.write( "Such a behavior repeats at each interval [\"n%2A%282pi%2F3%29\",\"%28n%2B1%29%2A%282pi%2F3%29\"], for all positive or negative integer numbers \"n\".\r\n" );
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document.write( "But the function with such a behavior can not have limits as x goes to +infinity or -infinity.\r\n" );
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document.write( "So, the given function has no limits as x goes to +infinity or -infinity.\r\n" );
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