VCE Specialist 3/4 Question Thread!

[speedy]

Could they give 'arg(z)' instead of 'Arg(z)' to trick people?

[Edward Elric]

Just curious why is the general solution to cosx=0 pi/2 + npi and not pi/2 + 2npi. I thought it had a period of 2 pi, so it should be solution + periodn, where n is an interger. Thoughts?

[Hiesenberg]

Could they give 'arg(z)' instead of 'Arg(z)' to trick people?

stupid question, but please simply explain the difference between the 2 and what steps we'd need to take, has been getting me in multiple choice

[keltingmeith]

Just curious why is the general solution to cosx=0 pi/2 + npi and not pi/2 + 2npi. I thought it had a period of 2 pi, so it should be solution + periodn, where n is an interger. Thoughts?

If you look at the graph, you can see that it actually repeats 0 twice in one period - and they're pi apart.

In fact, if you did only repeat every 2pi, you'd be missing half the solutions*

*Anybody who comes at me with "those two sets have the same cardinality" can go away.

[Mieow]

So how would proving a shape is a parallelogram differ from proving it is a rhombus with vectors?

[keltingmeith]

So how would proving a shape is a parallelogram differ from proving it is a rhombus with vectors?

Rhombus you have to show all sides are the same magnitude.

(also, this stuff is not on your exam, as it says in the study design. Might find it better to study other things)

[speedy]

stupid question, but please simply explain the difference between the 2 and what steps we'd need to take, has been getting me in multiple choice

Honestly, I'm not even that sure what arg(z) is :s

[Zealous]

Rhombus you have to show all sides are the same magnitude.

(also, this stuff is not on your exam, as it says in the study design. Might find it better to study other things)

Seriously. I thought vector proofs were assessible. Are trigonometric proofs assessible on the exams?

edit: only some vector proofs are on the study design, no fun.

[Ser_Asmodeus]

stupid question, but please simply explain the difference between the 2 and what steps we'd need to take, has been getting me in multiple choice

Might be wrong but arg(z) can be any angle that represents the complex number whereas Arg(z) is the angle between -pi inclusive to pi

[keltingmeith]

Seriously. I thought vector proofs were assessible. Are trigonometric proofs assessible on the exams?

edit: only some vector proofs are on the study design, no fun.

(Image removed from quote.)

Legit was just on there trying to find it. I swear a read somewhere that they can't be done, but it might just be my memory interpreting that weird.

[keltingmeith]

Might be wrong but arg(z) can be any angle that represents the complex number whereas Arg(z) is the angle between -pi inclusive to pi

Got it in one.
(or it's the other way around, can't remember. I haven't done complex in so long...)

[Mieow]

Seriously. I thought vector proofs were assessible. Are trigonometric proofs assessible on the exams?

edit: only some vector proofs are on the study design, no fun.

(Image removed from quote.)

omg I've never done the bottom two. How would I go about doing the last one? o.O

[Edward Elric]

If you look at the graph, you can see that it actually repeats 0 twice in one period - and they're pi apart.

In fact, if you did only repeat every 2pi, you'd be missing half the solutions*

*Anybody who comes at me with "those two sets have the same cardinality" can go away.

Oh yea that makes sense now, thank you

[speedy]

What do you guys use for finding the angle between vectors? Dot product? Or do separate angles with axis and minus them (basically needed for 2012 exam)? Does the latter always work?

[lolalol]

What do you guys use for finding the angle between vectors? Dot product? Or do separate angles with axis and minus them (basically needed for 2012 exam)? Does the latter always work?

I usually use dot product but if the cosine is something that doesn't easily give an angle (e.g. if it's cos(theta)=3/5) then I go for the separate angles thing.