document.write( "Question 1141440: Find the area of a triangle PQR, where P=(4,4,−1), Q=(3,3,1), and R=(3,−5,6) \n" ); document.write( "

Algebra.Com's Answer #762038 by Alan3354(69443) $\"\"$ $\"About$

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Find the area of a triangle PQR, where P=(4,4,−1), Q=(3,3,1), and R=(3,−5,6)
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\n" ); document.write( "A = PQ = (1,1,-2)
\n" ); document.write( "B = QR = (0,8,-5)
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\n" ); document.write( "Find the cross product of AB
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document.write( "|i   j   k|\r\n" );
document.write( "|1   1  -2|  ---> 11i + 5j + 8k = C\r\n" );
document.write( "|0   8  -5|\r\n" );
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\n" ); document.write( "\n" ); document.write( "Magnitude of C = $\"sqrt%2811%5E2+%2B+5%5E2+%2B+8%5E2%29+=+sqrt%28210%29\"$
\n" ); document.write( "Mag of C = area of parallelogram formed by A & B
\n" ); document.write( "Area of triangle is 1/2 of that
\n" ); document.write( "Area = $\"sqrt%28210%29%2F2\"$ sq units
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\n" ); document.write( "I haven't done one of those in decades.
\n" ); document.write( "I think that's right.
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