would we be penalised for...??? (1 Viewer)

[ninetypercent]

would we be penalised for:

- using the abbreviation rcis@ instead of r(cos@ + isin@)?
- not expressing a complex number in terms of its principle argument. e.g. when told to find the solutions to an equation, one writes cis(4pi/3) instead of cis(-pi/3)
- just writing cis(pi/2) when told to express "i" in mod-arg form. i.e. not showing the working out for how we obtained cis(pi/2)
- expressing mod-arg form in degrees instead of radians. e.g. cis(140 degrees, 30 minutes)

 

[pman]

most likely you would for the second2, not s aout thh fir 2 though

 

[ranganerd]

rcis(θ) is an acceptable way of showing complex numbers
r(cosθ +isinθ) is just to allow us to convert back to a+ib

you do need to write in terms of -π<x<π
i.e. you need to write -cis(π/3)

working out is always important

always use radians

 

[khorne]

would we be penalised for:

- using the abbreviation rcis@ instead of r(cos@ + isin@)?
- not expressing a complex number in terms of its principle argument. e.g. when told to find the solutions to an equation, one writes cis(4pi/3) instead of cis(-pi/3)
- just writing cis(pi/2) when told to express "i" in mod-arg form. i.e. not showing the working out for how we obtained cis(pi/2)
- expressing mod-arg form in degrees instead of radians. e.g. cis(140 degrees, 30 minutes)

1) No
2) No
3) No
4) No
Everything there is ok.

 

[madsam]

would we be penalised for:

- using the abbreviation rcis@ instead of r(cos@ + isin@)?
- not expressing a complex number in terms of its principle argument. e.g. when told to find the solutions to an equation, one writes cis(4pi/3) instead of cis(-pi/3)
- just writing cis(pi/2) when told to express "i" in mod-arg form. i.e. not showing the working out for how we obtained cis(pi/2)
- expressing mod-arg form in degrees instead of radians. e.g. cis(140 degrees, 30 minutes)

1. For the final answer i'd write it out in full, but for all working its fine
2. nope
3. If its only one mark, yeah for for your life, but if theres 2+ you should probably show working
4. why? Learn radians brah

 

[Trebla]

would we be penalised for:

- using the abbreviation rcis@ instead of r(cos@ + isin@)?
- not expressing a complex number in terms of its principle argument. e.g. when told to find the solutions to an equation, one writes cis(4pi/3) instead of cis(-pi/3)
- just writing cis(pi/2) when told to express "i" in mod-arg form. i.e. not showing the working out for how we obtained cis(pi/2)
- expressing mod-arg form in degrees instead of radians. e.g. cis(140 degrees, 30 minutes)

No for all of them, though for the last one it would be much more helpful to write the argument in radians when it comes to manipulating the mod-arg form.

 

[pman]

just ask your maths teacher instead of getting our mixed opinions

 

[xV1P3R]

In our 4unit exam last term, there was a question asking for you to express something in mod-arg form and apparently cis form isn't mod-arg form. So those who wrote cis lost marks, though you can use it in your working.

 

[ninetypercent]

what about in the actual hsc?

 

[Trebla]

In the actual HSC you would not be penalised for any of them.

 

[cutemouse]

I always used to write in the form z=cosθ+isinθ when it asked for mod-arg form. But I'd imagine that writing in the form z=cisθ would also be acceptable.