document.write( "Question 1087884: For sin a=-3/5 with terminal side in QIII and tan B=-5/12 with terminal side in QIV, find cos(a-B).\r
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\n" ); document.write( "a. -33/65
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Algebra.Com's Answer #702349 by Edwin McCravy(20060) $\"\"$ $\"About$

You can put this solution on YOUR website!

Draw a picture of the two given angles in their \r\n" );
document.write( "respective quadrants.  \r\n" );
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document.write( "Since , make the opposite side\r\n" );
document.write( "of the angle 'a' nearest the x-axis be the numerator of -3/5,\r\n" );
document.write( "which is -3, and the hypotenuse be the denominator of -3/5,\r\n" );
document.write( "which is 5.\r\n" );
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document.write( "Since , make the opposite side\r\n" );
document.write( "of the angle 'B' nearest the x-axis be the numerator of -5/12,\r\n" );
document.write( "which is -5, and the adjacent be the denominator of -5/12,\r\n" );
document.write( "which is 12.  Use the Pythagorean theorem to calculate the \r\n" );
document.write( "adjacent side of angle 'a' to be -4 (negative because it goes\r\n" );
document.write( "to the left.  Also use the Pythagorean theorem to calculate the \r\n" );
document.write( "hypotenuse of angle 'a' to be 13 (positive because the hypotenuse\r\n" );
document.write( "is the TERMINAL SIDE of the angles which is ALWAYS taken positive.  \r\n" );
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document.write( "Now use an identity for \r\n" );
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document.write( "   <--given\r\n" );
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document.write( "Substitute those values in\r\n" );
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document.write( "and simplify.  You finish.\r\n" );
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document.write( "Edwin

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