document.write( "Question 865766: Hi, could you please help me with the question (10ii) in the following exam paper. This is the link, thank you. \r
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Algebra.Com's Answer #521901 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
NOTE: Check my calculations, because it is way past my bedtime.
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\n" ); document.write( "The diagonals are
\n" ); document.write( "\"%22=%22\"\"%22%2B%22\"\"%22=%22\"\"%28i%2B3j%2B3k%29%2B%283i-j%2Bk%29=4i%2B2j%2B4k\"
\n" ); document.write( "AND
\n" ); document.write( "\"%22=%22\"\"%22-%22\"\"%22=%22\"\"%283i-j%2Bk%29-%28i%2B3j%2B3k%29=2i-4j-2k%29\"
\n" ); document.write( "So \"OB=sqrt%284%5E2%2B2%5E2%2B4%5E2%29=sqrt%2816%2B4%2B16%29=sqrt%2836%29=6\" and
\n" ); document.write( "\"AC=sqrt%282%5E2%2B4%5E2%2B2%5E2%29=sqrt%284%2B16%2B4%29=sqrt%2824%29=2sqrt%286%29\"
\n" ); document.write( "The diagonals bisect each other and split parallelogram OABC into 4 triangles.
\n" ); document.write( "Two sides of each triangle will be the halves of the two diagonals.
\n" ); document.write( "That is, two sides will have lengths of \"6%2F2=3\" and \"2sqrt%286%29%2F2=sqrt%286%29\" .
\n" ); document.write( "The remaining side of each triangle will be one side of the parallelogram, and not all sides of the parallelogram are the same length. (It is not a rhombus).
\n" ); document.write( "The parallelogram's side lengths are:
\n" ); document.write( "\"OA=sqrt%281%5E2%2B3%5E3%2B3%5E2%29=sqrt%281%2B9%2B9%29=sqrt%2819%29\"
\n" ); document.write( "\"OC=sqrt%283%5E3%2B1%5E2%2B1%5E2%29=sqrt%289%2B1%2B1%29=sqrt%2811%29\"
\n" ); document.write( "The angle between the sides measuring \"3\" and \"sqrt%286%29\" will be smaller in the two triangles where it is opposite the shorter parallelogram side measuring \"sqrt%2811%29\" .
\n" ); document.write( "We need the measure of that angle, that I will call \"theta\" .
\n" ); document.write( "The law of cosines, applied to that triangle says that
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\n" ); document.write( "\"11=9%2B6-6sqrt%286%29cos%28theta%29\"
\n" ); document.write( "\"6sqrt%286%29cos%28theta%29=9%2B6-11\"
\n" ); document.write( "\"6sqrt%286%29cos%28theta%29=4\"
\n" ); document.write( "\"cos%28theta%29=4%2F6sqrt%286%29\"
\n" ); document.write( "\"cos%28theta%29=2%2F3sqrt%286%29\"
\n" ); document.write( "\"cos%28theta%29=2sqrt%286%29%2F%283%2A6%29\"
\n" ); document.write( "\"cos%28theta%29=sqrt%286%29%2F9\" ---> \"theta=74.2%5Eo\"
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