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Edexcel Core 3 - 21st June 2016 AM

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Original post by Clovers
Can anyone please explain why the square root of e^-2x is e^-x Thanks :smile:

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e^{-2x} = 1 / e^{2x}

sqrt{ e^{-2x} ) = sqrt{ 1 / e^{2x} } = sqrt{1} / sqrt{ e^{2x}} = 1 / e^ {2x times 0.5} = 1/ e^{x}
Reply 81
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Clovers
2
Original post by Euclidean
e^{-2x} = 1 / e^{2x}

sqrt{ e^{-2x} ) = sqrt{ 1 / e^{2x} } = sqrt{1} / sqrt{ e^{2x}} = 1 / e^ {2x times 0.5} = 1/ e^{x}


Oh okay thanks

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Reply 82
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candol
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Original post by Clovers
Oh okay thanks

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or put another way
e^-2x = e^-x * e^-x
Reply 83
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Clovers
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Original post by candol
or put another way
e^-2x = e^-x * e^-x


Yeah :yy:

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Reply 84
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TeeEm
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http://www.thestudentroom.co.uk/showthread.php?t=3361867
Who really hates trig?
Original post by Thestudent98
Who really hates trig?


When I first saw it, it was very confusing :tongue: but having practiced so much it's really not too bad and there's nothing that can really throw you, as long as you think about what you can do, what identities you know, and if all else fails, get everything into sin and cos.
Original post by Thestudent98
Who really hates trig?


I DO!!!

Original post by SeanFM
When I first saw it, it was very confusing :tongue: but having practiced so much it's really not too bad and there's nothing that can really throw you, as long as you think about what you can do, what identities you know, and if all else fails, get everything into sin and cos.


Same here. I've actually learnt all the identities but occasionally i don't understand which one to use.
Original post by Student1408
I DO!!!



Same here. I've actually learnt all the identities but occasionally i don't understand which one to use.


If it helps, write out all of the trig identities you know down the side. You usually know what your goal is, so you have to look at which one would get you closest to that goal. If that doesn't work, try them all! Slightly time consuming but one of them has to work, unless you've gone wrong earlier on.
Original post by SeanFM
If it helps, write out all of the trig identities you know down the side. You usually know what your goal is, so you have to look at which one would get you closest to that goal. If that doesn't work, try them all! Slightly time consuming but one of them has to work, unless you've gone wrong earlier on.


That's a great idea but it would take time lol. I can do 'Prove' or 'show that' ones by doing a little of both sides and then meeting in the middle lol. Works for me.
Original post by Student1408
That's a great idea but it would take time lol. I can do 'Prove' or 'show that' ones by doing a little of both sides and then meeting in the middle lol. Works for me.


Yes, that's a good idea :tongue: but doesn't always work if you've got something very simple on the side you're supposed to finish on - eg tanx.
Original post by SeanFM
Yes, that's a good idea :tongue: but doesn't always work if you've got something very simple on the side you're supposed to finish on - eg tanx.


That's true. but you could put it in as one of the identities. For instance sin/cos or in another one :wink:
I love trig now, after lots and lots of practice :smile:
Original post by SaadKaleem
I love trig now, after lots and lots of practice :smile:


It is wonderful when you know what you are doing :h:
Reply 94
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TeeEm
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http://www.madasmaths.com/archive_iygb_practice_papers_c3_practice_papers.html
I'm at around 84-88 UMS right now ( I convert all the papers I do into UMS)
How do I get up to 90UMS?
My most common mistakes are wrongly sketching graphs or making algebraic slips when differentiating/solving


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Original post by Don Joiner
I'm at around 84-88 UMS right now ( I convert all the papers I do into UMS)
How do I get up to 90UMS?
My most common mistakes are wrongly sketching graphs or making algebraic slips when differentiating/solving


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I'm scoring around 92-94UMS. Most the mistakes to be honest that I make are just silly mistakes I do without thinking, my proper mistakes come from the functions chapter.

When sketching graphs involving transformations, try write the one or two co ordinates they give you down and apply the transformation on those co ordinates and take it from there.
With differentiating try and take it slowly if it's just algebraic mistakes you make. I'm moving onto Solomon Papers now that I'm happy with my scores. :smile:
Show that (tanθ×secθ)2−1cos2θ≡tan4θ−1(tan \theta \times sec \theta)^2 - \frac{1}{cos^2 \theta} \equiv tan^4 \theta - 1.
(edited 7 years ago)
Reply 98
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math42
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Original post by SeanFM
Show that sin2θcos4θ−1cos2θ≡tan4θ−1\frac{sin^2 \theta}{cos^4 \theta} - \frac{1}{cos^2 \theta} \equiv tan^4 \theta - 1.


I can do this one..
Original post by 1 8 13 20 42
I can do this one..


I would hope so :tongue:

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