Q15 · 2020 · Technology-freeSimple familiar6 marks
QUESTION 15 (6 marks)
The points O , A and C are represented in three-dimensional space in the diagram.
OABC forms a parallelogram in three-dimensional space.
a)[1 mark]
Determine the coordinates of B.
b)[1 mark]
M is the midpoint of BC. Determine the vector that represents .
c)[2 marks]
N divides AM in the ratio 2:1. Determine the vector that represents .
d)[2 marks]
Use a vector method to show that O, B and N lie on a straight line.
WORKED SOLUTION
6 marksQCAA guide · typeset solution
ANSWER
, , and .
Worked solution
a) , so .
b) The midpoint of BC is , so .
c) .
d) . The vectors are parallel with common point O, so O, B and N are collinear.
correctly determines the coordinates of B
determines vector
determines an expression for involving and the 1:2 ratio
determines vector
correctly communicates a requirement that O, B and N lie on a straight line
correctly demonstrates that the requirement has been met
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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