document.write( "Question 1114896: Given: cos (-105)
\n" ); document.write( "Find the exact value of the function without the use of a calculator.\r
\n" ); document.write( "\n" ); document.write( "I was unsure what to do with a negative, but from examples, I did the following where it \"ignores\" the negative.\r
\n" ); document.write( "\n" ); document.write( "cos (105) = cos (135 - 30)
\n" ); document.write( " $\"+cos+%28135%29+cos+%2830%29+%2B+sin+%28135%29+sin+%2830%29+\"$
\n" ); document.write( " $\"+%28-sqrt%282%29%2F2%29%28sqrt%283%29%2F2%29+%2B+%28sqrt%282%29%2F2%29%281%2F2%29+\"$
\n" ); document.write( " $\"+%28-sqrt%286%29%2F4%29%2B+%28sqrt%282%29%2F4%29+\"$
\n" ); document.write( "Final Answer: $\"+%28sqrt%282%29-sqrt%286%29%29+%2F+%284%29+\"$ \r
\n" ); document.write( "\n" ); document.write( "If the final answer is right, why does the (-) go away and if that procedure is incorrect how would you split up the -105? Thank you for any help! \n" ); document.write( "

Algebra.Com's Answer #729814 by ikleyn(52802) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "cos(a) = cos(-a) for any angle \"a\".\r\n" );
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document.write( "In particular,  cos(-105°) = cos(105°),  so your result is applicable to  cos(-105°).\r\n" );
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document.write( "Your final result is RIGHT:  cos(-105°) = .\r\n" );
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