document.write( "Question 601506: If f(x)= cos x and f(a)= -1/12 find the exact value of f(a) + f(a-2pi) + f(a+4pi) \n" ); document.write( "

Algebra.Com's Answer #379817 by jim_thompson5910(35256) $\"\"$ $\"About$

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Since cos(x+k*2pi) = cos(x) for any integer k, this means that cos(a-2pi) = cos(a) and cos(a+4pi) = cos(a)\r
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\n" ); document.write( "\n" ); document.write( "f(a) + f(a-2pi) + f(a+4pi) = f(a) + f(a) + f(a) = 3*f(a) = 3*(-1/12) = -3/12 = -1/4\r
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\n" ); document.write( "\n" ); document.write( "So f(a) + f(a-2pi) + f(a+4pi) = -1/4 \n" ); document.write( "

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