document.write( "Question 1114535: Unit vector which are perpendicular to vector 2i - j - 3k and lie in the plane of vector 7i - j - k and i + 5j - 3k \n" ); document.write( "
Algebra.Com's Answer #729948 by Fombitz(32388)\"\" \"About 
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Let A=(2,-1,-3), B=(7,-1,-1), C=(1,5,-3)
\n" ); document.write( "Find D that is coplanar to B and C and also perpendicular to A.
\n" ); document.write( "Coplanar means that
\n" ); document.write( "\"D=p%2AB%2Bq%2AC\" where \"p\" and \"q\" are two scalars.
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\n" ); document.write( "Perpendicular means that \"A%2AD=0\"
\n" ); document.write( "\"A%2A%28pB%2BqC%29=0\"
\n" ); document.write( "\"2%287p%2Bq%29%2B%28-1%29%28-p%2B5q%29%2B%28-3%29%28-p-3q%29=0\"
\n" ); document.write( "\"%2814p%2B2q%29%2B%28p-5q%29%2B%283p%2B9q%29=0\"
\n" ); document.write( "\"18p%2B6q=0\"
\n" ); document.write( "\"3p%2Bq=0\"
\n" ); document.write( "\"q=-3p\"
\n" ); document.write( "So then,
\n" ); document.write( "\"D=p%2AB-3p%2AC\"
\n" ); document.write( "D=p(2,-1,-3)-3p(1,5,-3)
\n" ); document.write( "D=(2p,-p,-3p)+(-3p,-15p,9p)
\n" ); document.write( "D=(-p,-16p,6p)
\n" ); document.write( "To find the unit vector, divide by the magnitude of the vector,
\n" ); document.write( "\"abs%28D%29=sqrt%28%28-p%29%5E2%2B%28-16p%29%5E2%2B%286p%29%5E2%29\"
\n" ); document.write( "\"abs%28D%29=sqrt%28p%5E2%2B256p%5E2%2B36p%5E2%29\"
\n" ); document.write( "\"abs%28D%29=sqrt%28293p%5E2%29\"
\n" ); document.write( "\"abs%28D%29=sqrt%28293%29p\"
\n" ); document.write( "Dividing,
\n" ); document.write( "\"D%5Bu%5D=D%2Fabs%28D%29\"
\n" ); document.write( "\"D%5Bu%5D\"=(\"-p%2F%28sqrt%28293%29p%29\",\"%28-16p%29%2F%28sqrt%28293%29p%29\",\"%286p%29%2F%28sqrt%28293%29p%29\")\r
\n" ); document.write( "\n" ); document.write( "\"D%5Bu%5D\"=(\"-1%2F%28sqrt%28293%29%29\",\"-16%2F%28sqrt%28293%29%29\",\"6%2F%28sqrt%28293%29%29\")
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