2013 SRJC P1 Q8

2013 SRJC P1 Q8

8 marks
Prelims

The points \(A\) and \(B\) are equidistant from the origin, \(O\) and have position vectors a and b (referred to O) such that the acute angle \(AOB\) is \(\frac{\pi }{4}\). The point \(N\) on \(AB\) is such that \(AN:NB=1:2\) and the point \(M\) is the foot of perpendicular of \(N\) on \(OB\).

  1. Show that the position vector of point \(M\) is \(\frac{\left( 1+\sqrt{2} \right)}{3}\mathbf{b}\).[4]
  2. Given that \(\mathbf{b}\) is a unit vector, find the exact area of \(\Delta OMN\).[4]

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Answer:(i) \(\overrightarrow{OM}=\dfrac{1+\sqrt2}{3}\mathbf b\) (ii) \(\dfrac{\sqrt2+2}{18}\) units\(^2\)

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