Siddardha Reddy Sanagala's answer to Bri's Junior College 1 H2 Maths Singapore question.
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The final answer for (iii) is (-5,11,9) btw in case that is confusing.
Hope it helps :)
Hope it helps :)
Date Posted:
1 year ago
(i)
question says "... find the unit vector(s)...".
answer should be + & - of the answer you gave, as the unit vector in the reverse direction also qualify as being parallel.
(iii)
firstly, the drawing of the parallelogram is incorrect. when naming any polygon, you need to take the vertices consecutively in one direction either clockwise or anti-clockwise, so you need to interchange your points C & D.
secondly, here is a much easier method to find position vector of D ...
since ABCD is a parallelogram, then ...
vector CD = vector BA
vector OD - vector OC = vector OA - vector OB
vector OD = vector OA - vector OB + vector OC
= (4 -9 -1) - (1 3 5) + (-2 -1 3)
= (1 -13 -3)
where (1 -13 -3) represents the column vector with x=1, y=-13, z= -3.
[sorry, but this comment formatting does not allow printing of vertical column vectors].
question says "... find the unit vector(s)...".
answer should be + & - of the answer you gave, as the unit vector in the reverse direction also qualify as being parallel.
(iii)
firstly, the drawing of the parallelogram is incorrect. when naming any polygon, you need to take the vertices consecutively in one direction either clockwise or anti-clockwise, so you need to interchange your points C & D.
secondly, here is a much easier method to find position vector of D ...
since ABCD is a parallelogram, then ...
vector CD = vector BA
vector OD - vector OC = vector OA - vector OB
vector OD = vector OA - vector OB + vector OC
= (4 -9 -1) - (1 3 5) + (-2 -1 3)
= (1 -13 -3)
where (1 -13 -3) represents the column vector with x=1, y=-13, z= -3.
[sorry, but this comment formatting does not allow printing of vertical column vectors].
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