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# Edexcel Core 3 - 21st June 2016 AM watch

1. how to prove the sinA+sinB= 2sin(A+B)/2 cos(A-B)/2 ?

Do i even need to know about these formulae???
Easy way to work out domain and range?
sketch the curve. See where f(x)/y is highest/lowest.
3. (Original post by Wee chump)
how to prove the sinA+sinB= 2sin(A+B)/2 cos(A-B)/2 ?

Do i even need to know about these formulae???
ikr. I dont even know when or where to use em.
4. (Original post by Wee chump)
how to prove the sinA+sinB= 2sin(A+B)/2 cos(A-B)/2 ?

Do i even need to know about these formulae???
Use general expansion of sin(x + y), noting that A = (A+B)/2 + (A-B)/2 and noting a similar expression for B
5. (Original post by SeanFM)
Ha, I see, that must have been very confusing indeed. It is C4 stuff. Confusing if you've never seen it before but alright when you get the hang of it.

6. (Original post by SeanFM)

For the first part of the question, find x and go from there.

test
test
I'm going to be honest here: I'm confused. Like, I have no clue XD

EDIT: Wait...gimme a sec!!
7. (Original post by yuveethini)
I can't see a typing error - part b is possible to answer. what have you tried?
8. SeanFM I got e^y = x from y = lnx. Then subbing it into log2x I get log2(e^y)...
9. (Original post by Don Pedro K.)
SeanFM I got e^y = x from y = lnx. Then subbing it into log2x I get log2(e^y)...
See, you can do it, you just need to not give up.
10. (Original post by SeanFM)
See, you can do it, you just need to not give up.
Yay ! Thanks Sean
11. (Original post by SeanFM)
I can't see a typing error - part b is possible to answer. what have you tried?
Yes i have, plus the mark scheme says sinX replaces 2sinXcosX (letting X=x/2), as well as cosX to 1-2sin^2X.
But then i think i just figured it out, however isnt sinX= sinx(x/2)cos(x/2)?
12. (Original post by yuveethini)
Yes i have, plus the mark scheme says sinX replaces 2sinXcosX (letting X=x/2), as well as cosX to 1-2sin^2X.
But then i think i just figured it out, however isnt sinX= sinx(x/2)cos(x/2)?
sin2x = 2sinxcosx

Therefore,

sinx = 2sin(x/2)cos(x/2)
13. (Original post by yuveethini)
Yes i have, plus the mark scheme says sinX replaces 2sinXcosX (letting X=x/2), as well as cosX to 1-2sin^2X.
But then i think i just figured it out, however isnt sinX= sinx(x/2)cos(x/2)?
Allllmost.

Remember that sin2y = 2sinycos, and you can just replace x by anything (eg in the case above, 2y = x.
14. (Original post by Don Pedro K.)
Yay ! Thanks Sean
SeanFM This is what the mark scheme says ?

15. June 2015 questions 2b, draw the equation of asymptote for modulus of fx.
If you take y=5 it cuts the graph, and graphs do not cut their asymptotes, can someone explain this please?

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16. (Original post by Don Pedro K.)
SeanFM This is what the mark scheme says ?

it seems that they've applied the change of base formula.

Where one of the terms is log to base e, otherwise known as ln.

What question is this from? It's been said that it's not on the spec (which I believe), even though it's in the C2 textbook.
17. question.
if you change the angles inside the double angle identity. for sin(2A) which is 2sinAcosA. if its sin4A.is it 4sin2Acos2A?or 2sin2Acos2A
18. (Original post by bat_man)
question.
if you change the angles inside the double angle identity. for sin(2A) which is 2sinAcosA. if its sin4A.is it 4sin2Acos2A?or 2sin2Acos2A
It's always 2* if you're halving the angle, no matter what you're halving.
19. (Original post by SeanFM)
it seems that they've applied the change of base formula.

Where one of the terms is log to base e, otherwise known as ln.

What question is this from? It's been said that it's not on the spec (which I believe), even though it's in the C2 textbook.
It's from Solomon Paper D

https://b3755649dbd1afe3db91a899c3b9...%20Edexcel.pdf

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