Maths - HL Proofs Poll

electrictrad

The proofs are usually a small part of the paper, and doable without study. . .but only if you're pretty good at LC HL Maths. . .

So. . .3 days to go. What dye think's coming up?

PJelly

Integration, do cone and sphere.
Quotient rule because it's never been asked.
I read somewhere that Prove LogAB=LogA+LogB might come up
And make sure you know the perpendicular distance from a line, it's a full part C. And with the way the marking is going, that means 20/25 or even 30 marks.

electrictrad

PJelly wrote: »

I read somewhere that Prove LogAB=LogA+LogB might come up

How do you prove that?

Can you just equate them, then bring logB over to the other side, and use log x - log y = log x/y

PJelly

It took me a while, but it's like this.
Let, X^u (or anything) = a => LogxA=U
let X^v = B => LogxB = V
let X^n = AB => LogxAB = N

AB =B.A
Therefore, from above, X^n= X^u . X^v
= X^n =X^u+v
Which implies.. N= U+V as they all have the base X
And again from above, this implies, LogxAB=LogxA +LogxB

Same for LogA/B=LogA-LogB, except you say A/B=A divided by B
which implies X^n= X^u (divided by) X^v Etc and so on

electrictrad

I getya. . .thats clever. . .can you then use logs to prove the inverse?