Sec, Cosec & Cot

[Shark 774]

My teacher said today that we have to "be aware" of the double angle rules and sec, cosec and cot. When I asked him if they could be on the upcoming sac he said maybe. But these things aren't even in the methods course outline (double angle might be, but sec etc. definitely aren't). Any ideas? Is he just bluffing? What if he does actually put it on there and nobody knows it apart from the specialist kids??

[david10d]

the double angle rules are still the same.

eg. 1/cos(2x) = 1/(cos^2(x)-sin^2(x))

EDIT: LOL, I just read op.

sec(x)=1/cos(x) cosec(x)=1/sin(x) cot=1/tan(x)

It's easy to memorise those. Double angle formulas are definitely not in the Methods course..

What kind of sac is this?

[taiga]

Your teacher is a rascal =\

[jane1234]

Your teacher is right in that you need to be aware of the double angle formulas. It says so in the study design. However, you don't need to know how to use them specifically, rather just be able to recognise that sin(2x) may also be written as 2sin(x)cos(x).
You definitely don't need to cosec or cot.
We had to learn what sec was only to be able to recognise the derivative of tan(x) in either form.
That said, your teacher would be horrible to test you on cosec or cot, or even applying sec and double-angled formulas (because you only need to recognise them).

• logarithm laws and exponent laws, recognition of equivalent forms using compound and double
angle formulas for sine, cosine and tangent;

From http://www.vcaa.vic.edu.au/vce/studies/mathematics/mathsstd.pdf

[Shark 774]

the double angle rules are still the same.

eg. 1/cos(2x) = 1/(cos^2(x)-sin^2(x))

EDIT: LOL, I just read op.

sec(x)=1/cos(x) cosec(x)=1/sin(x) cot=1/tan(x)

It's easy to memorise those. Double angle formulas are definitely not in the Methods course..

What kind of sac is this?

This is some application SAC that goes for 5 periods and we work in groups that are chosen at random (which is another stupid idea from my teacher, totally unfair I reckon!). The SAC is on logs/exponential, circular functions and cubics/quartics.

[GuessWho]

I'm fairly sure that you will need to at least know how to use all the double angle formulas. As for the inverse circular functions, you won't need to know them for methods.

[david10d]

That's strange.. When do double angles come up in methods? :s Just general knowledge?