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Question 7

With respect to a fixed origin OOO, a research drone is monitoring a straight-line path l1l_1l1​ given by the equation

r=(−325)+μ(21−2) \mathbf{r} = \begin{pmatrix} -3 \\ 2 \\ 5 \end{pmatrix} + \mu \begin{pmatrix} 2 \\ 1 \\ -2 \end{pmatrix} r=​−325​​+μ​21−2​​

where μ\muμ is a scalar parameter.

The point AAA represents a specific checkpoint on l1l_1l1​. Given that ∣OA→∣=70|\overrightarrow{OA}| = \sqrt{70}∣OA∣=70​.

a.

Show that at AAA, the parameter μ\muμ satisfies

9μ2−28μ−32=0 9\mu^2 - 28\mu - 32 = 0 9μ2−28μ−32=0
[4]
b.

(i) Show that one possible position vector for AAA is 5i+6j−3k5\mathbf{i} + 6\mathbf{j} - 3\mathbf{k}5i+6j−3k. (ii) Find the other possible position vector for AAA.

[3]
c.

The path l2l_2l2​ is parallel to l1l_1l1​ and passes through the origin OOO. Given that:

  • OA→=5i+6j−3k\overrightarrow{OA} = 5\mathbf{i} + 6\mathbf{j} - 3\mathbf{k}OA=5i+6j−3k
  • Point BBB lies on l2l_2l2​ where ∣OB→∣=15|\overrightarrow{OB}| = 15∣OB∣=15

Find the area of triangle OABOABOAB, giving your answer to one decimal place.

[5]

Vectors Questions

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