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# Edexcel Core 3 - 21st June 2016 AM watch

1. (Original post by N_ght.yo)
I know it's a core 1 question but a mistake I slip up on everytime: what order do you perform a graph transformation i.e: stretch or translation first??
I always do what's in the brackets first! That seems to work every time >.>!
2. SeanFM Is the range of arctan(x) -90 <= x <= 90 or -90 < x < 90?
3. (Original post by Don Pedro K.)
SeanFM Is the range of arctan(x) -90 <= x <= 90 or -90 < x < 90?
I would say that it is undefined at 90 and -90.
4. (Original post by Ainsleyy)
Hey guys for question 2b in C3 SOLOMON E I keep finding that for questions like that I end up with only the tanx = 2 solution and I dont end up with the cos2x = 0 solutions. I think this is because im dividing both sides by cos2x. Is there something im missing? Or should I just remember to never divide both sides by cos etc?
Hey, I used to do this all the time. All you have to remember is rather than divide just factorise instead as if you divide by a trig function you'll be losing some solutions
5. (Original post by Jold)
Hey, I used to do this all the time. All you have to remember is rather than divide just factorise instead as if you divide by a trig function you'll be losing some solutions
You may have just saved me several marks!! Thank you so much!!
6. guyss need help http://www.madasmaths.com/archive/iy...apers/c3_f.pdf question 8c) the range. How did they get o<f(x)<4 ?? I dont see it. Why am I getting every mark on c3 papers apart from the range questions
7. also guys should we know the graphs for sec/cosec/cotx (well you can work them out easily enough but still..)
8. ...

I'm sorry, what the heck?
9. (Original post by Don Pedro K.)
...

I'm sorry, what the heck?
Quite a difficult question, I would be happy if I got 1 mark from in it in the real exam!
10. (Original post by Don Pedro K.)
...

I'm sorry, what the heck?
That's quite a nice problem. I'm sure the vid explains it well, exam solutions is usually excellent
11. (Original post by Jold)
Hey, I used to do this all the time. All you have to remember is rather than divide just factorise instead as if you divide by a trig function you'll be losing some solutions
Thank you man that helps alot
12. (Original post by 13 1 20 8 42)
That's quite a nice problem. I'm sure the vid explains it well, exam solutions is usually excellent
Yeah he does explain it really well but the problem is that I would NEVER get that xD Please tell me this is not normal maths lol???

(Original post by ryandaniels2015)
Quite a difficult question, I would be happy if I got 1 mark from in it in the real exam!
Loool I would just skip it I think XD
13. (Original post by Don Pedro K.)
Yeah he does explain it really well but the problem is that I would NEVER get that xD Please tell me this is not normal maths lol???

Loool I would just skip it I think XD
or that XD!!
14. (Original post by Don Pedro K.)
Yeah he does explain it really well but the problem is that I would NEVER get that xD Please tell me this is not normal maths lol???

Loool I would just skip it I think XD
This is not going to come up in C3, or at least it is incredibly unlikely. However it is "normal maths" in one sense. It nicely illustrates part of the relationship between cos and sin.
15. (Original post by 13 1 20 8 42)
This is not going to come up in C3, or at least it is incredibly unlikely. However it is "normal maths" in one sense. It nicely illustrates part of the relationship between cos and sin.
Yeah the video is really good and I understand what is going on. If only I could deduce that myself xD
16. So what nasty question (or standard question but with a twist) do you reckon Edexcel will throw in apart from the usual ones that always come up?

any thoughts?

also are there any small parts of the spec that are easy to neglect but could come up?
17. (Original post by gekkelekkebekke)
So what nasty question (or standard question but with a twist) do you reckon Edexcel will throw in apart from the usual ones that always come up?

any thoughts?

also are there any small parts of the spec that are easy to neglect but could come up?
tricky trig
Remember, putting things in terms of sin and cos often helps, you can always change 1 to sin^2x + cos^2x, and you should generally start from the more complicated side and work to simplify and get the other. And be very very intimate with trig identities, know them well

rambunctious range
Remember, consider endpoints of the domain, and consider turning points. These are pretty much all you need. Don't forget that the domain of the function is the range of its inverse (if it has one) and vice versa

awful arcs
If I recall correctly inverse trigonometric functions are on the spec but barely ever seem to be used. So, with the current syllabus in its death throes, they might fancy throwing them in. Being familiar with the graphs is important, but more important is to understand what's going on, and realise that they can only be defined on a limited domain due to the one-to-one requirement. Remember to sketch inverse functions accurately you just need to reflect the original function in the line y = x

devilish differentiation
Rarely does a nasty question on this come up, but it did in 2013. You just need to be very, very methodical. There are lots of rules to apply, and if a horrible expression comes up, it can seem a bit overwhelming, but just take it all one step at a time, and practice certainly makes perfect in this area.

The other sections are generally straightforward.
18. Guys I have an issue I can't do any function questions when they ask me to find the range someone advise me or give me tips haha
19. (Original post by Valyrian)
Guys I have an issue I can't do any function questions when they ask me to find the range someone advise me or give me tips haha
if the domain is given on the graph just put those values into f(x) for the range. also look for any asymptotes.
20. Hey,

Here's a nice little identity similar to the arcsin(x) + arccos(x) relation. See if you can prove it . You can find it attached since tsr latex seems to be failing me...
Attached Images
21. untitled-1.pdf (38.5 KB, 119 views)

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