A-level Mathematics/MEI/FP1/Complex Numbers/argand diagram answers

z=20+0j

wanted form =

z=r(cos\theta +jsin\theta )

r={\sqrt {20^{2}+0^{2}}}=20

tan({0 \over 20})=0

z=20(cos(0)+jsin(0))

z=0+12j

wanted form =

z=r(cos\theta +jsin\theta )

r={\sqrt {(}}{0^{2}+12^{2}})=12

tan({12em \over 0})=\infty

tan^{-1}(\infty )={\pi  \over 2}

- You need to look at the graph to get this really. Using Sine or Cosine may be advisable in this situation.

z=12(cos({\pi  \over 2})+jsin({\pi  \over 2}))

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