sin3@ - State or Prove? (1 Viewer)

[kpq_sniper017]

If there's a trig. proof in an Ext 1 exam involving sin/cos/tan3@, do you have to expand it to get full marks? or can you just state the result?
since the triple angle formulae aren't explicitly on the Ext 1 syllabus (or are they?), would u have to expand them??

 

[George W. Bush]

Depends on the question, of course.

Most of the questions I have seen (and I am not that well versed in this area) have derive the sin/cos/tan 3@ results in part a or b, and then a question which requires the use of them.

 

[Xayma]

I would expand it, but if you know it, it makes it alot easier, since you could skip steps in the working, but aslong as you make it clear you expanded it.

 

[CM_Tutor]

I would put in the derivation - to skip it would be very dangerous, marks wise.

 

[:: ck ::]

are we allowed to use demoivre's for 3u when deriving these expansions?

 

[Xayma]

For 3unit you are unlikely to get anything greater then sin/tan/cos 3@ so it would probably be as quick to expand it (and you dont have to put, equating real and imaginary etc)

 

[SimGhost]

We had a question to expand that in our the prelim courseexam.

Some people didn't put in the expansion steps, and they lost marks.

 

[kpq_sniper017]

ok...
i'll probably derive it first to be on the safe side - i'd have to agree with george w. now that i think about it.
they often ask u to expand it in the first part first beofre applying it in the second part.

 

[untamedanimal]

CHeck how much its worth, if its only 1 mark then you wont have to derive it

 

[Affinity]

ryan:
using demoivre for this is superfluous.

 

[:: ck ::]

lol ok

me just tryin to sound like a smartass aahha