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# Surds Tweet

Maths and statistics discussion, revision, exam and homework help.

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1. Surds
Hi, how do I rationalise this

From the sum formula for tan I get as far as

Then it's a mystery after cancelling the quarters.

Maybe I should have worked out the tan values rather than going down the sin cos route?

But it'd still be good to know what to do

Maybe I am supposed to multiply the whole thing by ?
Last edited by SubAtomic; 23-07-2012 at 17:29.
2. Re: Surds
Multiply by \displaystyle\dfrac{\sqrt 2 + \sqrt 6}{\sqrt 2 + \sqrt 6} I think.
3. Re: Surds
So I end up with

Am I doing this right? Sign error?
Last edited by SubAtomic; 23-07-2012 at 17:41.
4. Re: Surds
Also could I suggest you buy a Casio Natural Display calculator as this will rationalise denominators for you?
5. Re: Surds
(Original post by Mr M)
That step is correct. Rationalise again.
?
Last edited by SubAtomic; 23-07-2012 at 17:46.
6. Re: Surds
(Original post by Mr M)
Also could I suggest you buy a Casio Natural Display calculator as this will rationalise denominators for you?
Yes I have one but am doing it by hand

7. Re: Surds
(Original post by SubAtomic)
Hi, how do I rationalise this

From the sum formula for tan I get as far as

Then it's a mystery after cancelling the quarters.

Maybe I should have worked out the tan values rather than going down the sin cos route?

But it'd still be good to know what to do

Maybe I am supposed to multiply the whole thing by ?
Much quicker to multiply the whole thing by

...
8. Re: Surds
(Original post by Lord of the Flies)
Much quicker to multiply the whole thing by

...
Yes, I thought that was what he put in the first place after he edited!

OP just use your calculator or revise rationalising denominators from your Core 1 textbook.
9. Re: Surds
(Original post by Lord of the Flies)
Much quicker to multiply the whole thing by

...
10. Re: Surds
(Original post by SubAtomic)
Hum, yes?...
11. Re: Surds
(Original post by Mr M)
Yes, I thought that was what he put in the first place after he edited!

OP just use your calculator or revise rationalising denominators from your Core 1 textbook.
Yeah I kinda forgot what I was doing until I typed it up, C1 Never did it, all OU maths.
12. Re: Surds
Thats what I said I think he should get

8+4(root3)/ -4
13. Re: Surds
(Original post by Lord of the Flies)
Hum, yes?...
Wasn't questioning was just typing. Can see how that'd be the logical thing to do
14. Re: Surds
(Original post by SubAtomic)
Yeah I kinda forgot what I was doing until I typed it up, C1 Never did it, all OU maths.
Ok just go back and do it again.

Use your knowledge of the difference of two squares to reduce working.
15. Re: Surds
(Original post by FrescoDiMorte)
Thats what I said I think he should get

8+4(root3)/ -4
Surely that simplies further?
16. Re: Surds
(Original post by Mr M)
Surely that simplies further?
Certainly does,
17. Re: Surds
(Original post by SubAtomic)
Certainly does,

Which OU module is this?
18. Re: Surds
(Original post by Mr M)
Surely that simplies further?
-2-root3/1
19. Re: Surds
(Original post by Mr M)

Which OU module is this?
It is a part of MS221 on trig formulas, when I look in the back of the book it seems I went the long way around by using the sin cos vals instead of using tan vals straight away. No mention of whether to use a calculator or not, just assumed as per.

Never did much with surds at GCSE, or at OU on 123 or 121, soon forget stuff if I don't keep up with the practice.

Thanks people
Last edited by SubAtomic; 23-07-2012 at 18:09.
20. Re: Surds
(Original post by SubAtomic)
It is a part of MS221 on trig formulas, when I look in the back of the book it seems I went the long way around by using the sin cos vals instead of using tan vals straight away. No mention of whether to use a calculator or not, just assumed as per.
My wife did that module a few years ago. You are allowed a calculator in the exam.