Maths Paper 2 Proofs (HL)

zam

In my revision book it has a list of the proofs at the front and it says:

Tangent Theorem
Angle Between Two Lines Formula
Perpendicular Distance Formula
Difference Equation Theorem

Yet I heard someone mention that we need to know the Cosine Rule as well? Are there any other proofs not listed here that I need to know?
Thanks!

Killio9

well there are the trig proofs arent there? Cos(a+b) cos (A-B) that sorta thing? thinkin cosine rule is in there with them..

shi7zman

the cos(A-B) is not on syllabus but the cos(A+B) is. along with that there are 11 other trig proofs. most are simple enough.

**Timbuk2**

To prove Cos(A+B) you need to first prove Cos(A-B) and replace the B with -B. Similarly, for Sin you replace the A with 90-A

zam

Forgot about the trig proofs/identities but sure. Anything else other than that? Looks like I better get studying...

shi7zman

**Timbuk2** wrote: »

To prove Cos(A+B) you need to first prove Cos(A-B) and replace the B with -B. Similarly, for Sin you replace the A with 90-A

They wont ask to prove cos(A-B), so if you are told to prove A+B you can just take A-B from the tables

**Timbuk2**

shi7zman wrote: »

They wont ask to prove cos(A-B), so if you are told to prove A+B you can just take A-B from the tables

Then why is there that proof in the book with the unit circle, and getting the distance twice??

DancingQueen:)

**Timbuk2** wrote: »

Then why is there that proof in the book with the unit circle, and getting the distance twice??

It came up at a marking conference recently and we don't need to know the first part. My teacher said you didn't have to do that part, that you can just start from Cos(A-B) and get full marks.

Indigo Sunrise

What's the tangent theorem?

zam

Indigo Sunrise wrote: »

What's the tangent theorem?

prove that xx1 + yy1 = r^2 is a tangent to the circle x^2 + y^2 = r^2 at (x1,y1)

Indigo Sunrise

Oh yeah, I know that. Thanks.

**Timbuk2**

DancingQueen:) wrote: »

It came up at a marking conference recently and we don't need to know the first part. My teacher said you didn't have to do that part, that you can just start from Cos(A-B) and get full marks.

Well that's excellent

Indigo Sunrise wrote: »

What's the tangent theorem?

The circle one: xx1 + yy1 = r^2 or something similar

SantryRed

Whole day cramming session for this paper starts at 12 for me. Haven't done a tap on paper 2 in ages.

DancingQueen:)

**Timbuk2** wrote: »

Well that's excellent

It is indeed! Atleast it cuts down on a bit of the work.

SantryRed wrote: »

Whole day cramming session for this paper starts at 12 for me. Haven't done a tap on paper 2 in ages.

I've been up since 8 just doing maths, I really don't like Paper 2 so it's going to be a hard day : (

MathsManiac

shi7zman wrote: »

They wont ask to prove cos(A-B), so if you are told to prove A+B you can just take A-B from the tables

That is not allowed.

The identities are taken in the order that they appear in the syllabus. You're allowed to assume any of the formulae that come before the one you're trying to prove, but you're not allowed to use any of the ones that come after it (or ones that aren't on the list at all).

The syllabus is on the Dept. of Education's website. Here it is:
http://www.education.ie/servlet/blobservlet/lc_maths_sy.pdf?language=EN
You need to be able to prove formulae 1 to 12 in the appendix on page 19.

Scoobydooo

I know for certain proofs on paper II there's easier versions of the proofs available than the ones in our book, does anyone have a link to any of these ?

shi7zman

Scoobydooo wrote: »

I know for certain proofs on paper II there's easier versions of the proofs available than the ones in our book, does anyone have a link to any of these ?

theres a good version of them on www.cnocmhuiregranard.ie/proofs.pdf

CantStandMeNow

shi7zman wrote: »

theres a good version of them on www.cnocmhuiregranard.ie/proofs.pdf

Ah that's perfect