3.42: Vector line XYZXYZ in triangle OABOAB

0606/13/O/N/23 — Question 11 · 9 marks

3.42 diagram3.42 diagram
(a)
In triangle OABOAB, OA=a\overrightarrow{OA}=\mathbf{a}, OB=b\overrightarrow{OB}=\mathbf{b}. The line XYZXYZ satisfies OX=45b\overrightarrow{OX}=\tfrac{4}{5}\mathbf{b}, AY=13AB\overrightarrow{AY}=\tfrac{1}{3}\overrightarrow{AB}, AZ=na\overrightarrow{AZ}=n\mathbf{a}, and YZ=mXY\overrightarrow{YZ}=m\overrightarrow{XY}.
Show that XY=23a715b\overrightarrow{XY}=\dfrac{2}{3}\mathbf{a}-\dfrac{7}{15}\mathbf{b}.
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(b)
Find YZ\overrightarrow{YZ} in terms of mm, a\mathbf{a} and b\mathbf{b}.
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(c)
Find YZ\overrightarrow{YZ} in terms of nn, a\mathbf{a} and b\mathbf{b}.
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(d)
Hence find the values of mm and nn.
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