[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 ?

[FrescoDiMorte]

Multiply by \displaystyle\dfrac{\sqrt 2 + \sqrt 6}{\sqrt 2 + \sqrt 6} I think.

[SubAtomic]

So I end up with







Am I doing this right? Sign error?

[Mr M]

Also could I suggest you buy a Casio Natural Display calculator as this will rationalise denominators for you?

[SubAtomic]

(Original post by Mr M)
That step is correct. Rationalise again.

?

[SubAtomic]

(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

Good idea bad idea?

[Lord of the Flies]

(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

...

[Mr M]

(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.

[SubAtomic]

(Original post by Lord of the Flies)
Much quicker to multiply the whole thing by

...

[Lord of the Flies]

(Original post by SubAtomic)

Hum, yes?...

[SubAtomic]

(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.

[FrescoDiMorte]

Thats what I said I think he should get

8+4(root3)/ -4

[SubAtomic]

(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

[Mr M]

(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.

[Mr M]

(Original post by FrescoDiMorte)
Thats what I said I think he should get

8+4(root3)/ -4

Surely that simplies further?

[SubAtomic]

(Original post by Mr M)
Surely that simplies further?

Certainly does,

[Mr M]

(Original post by SubAtomic)
Certainly does,

which is the correct answer.

Which OU module is this?

[FrescoDiMorte]

(Original post by Mr M)
Surely that simplies further?

-2-root3/1

[SubAtomic]

(Original post by Mr M)
which is the correct answer.

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

[Mr M]

(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.