document.write( "Question 1083103: (b) Show that the vectors P = 3i – 2j + k, Q = i – 3j + 5k, and R = 2i + j – 4k form a right angled triangle.
\n" ); document.write( "(c) Use vectors in (b) above to evaluate P Q and R Q what do these two final vectors represent
\n" ); document.write( ".thank you
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Algebra.Com's Answer #698042 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
The sum of two vectors must equal the other vector,
\n" ); document.write( "\"PQ%2BQR=PR\"
\n" ); document.write( "So then,
\n" ); document.write( "\"PQ=OP-OQ\"
\n" ); document.write( "\"QR=OQ-OR\"
\n" ); document.write( "\"PR=OP-OR\"
\n" ); document.write( "where O stands for the origin,
\n" ); document.write( "So,
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\n" ); document.write( "\"PQ=+%28matrix%281%2C5%2C2%2C%22%2C%22%2C1%2C%22%2C%22%2C-4%29%29\"
\n" ); document.write( ".
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\n" ); document.write( "\"QR=+%28matrix%281%2C5%2C-1%2C%22%2C%22%2C-4%2C%22%2C%22%2C9%29%29\"
\n" ); document.write( ".
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\n" ); document.write( "\"PR=+%28matrix%281%2C5%2C1%2C%22%2C%22%2C-3%2C%22%2C%22%2C5%29%29\"
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\n" ); document.write( "And,
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\n" ); document.write( "\"PQ%2BQR=%28matrix%281%2C5%2C1%2C%22%2C%22%2C-3%2C%22%2C%22%2C5%29%29\"
\n" ); document.write( "\"PQ%2BQR=PR\"
\n" ); document.write( "So the two vectors do add up to the third.
\n" ); document.write( "Additionally, two of the vectors must be perpendicular to each other in order for that to happen.
\n" ); document.write( "So check the dot products,
\n" ); document.write( "\"P%2AQ=3%281%29%2B%28-2%29%28-3%29%2B1%285%29=3%2B6%2B5=14\"
\n" ); document.write( "\"Q%2AR=1%282%29%2B%28-3%29%281%29%2B5%28-4%29=2-3-20=-21\"
\n" ); document.write( "\"P%2AR=3%282%29%2B%28-2%29%281%29%2B1%28-4%29=6-2-4=0\"
\n" ); document.write( "Since the dot product is zero, the two vectors are perpendicular (right angle) and together with the result above it proves that the vectors form a right triangle.
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