Edexcel Core 3 - 21st June 2016 AM

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Original post by ryandaniels2015

When solving trig equations do u have to show the cast or graph or can u calculate by 360-ans, etc etc

There isn't ever any method marks for the additional solutions, you find the first one and you can just write down all the others.

Reply 981

username1529975

Original post by selenmer

Can anyone please help me do this trig proof? Thank you :smile:

How tf? Is this C3? I've not got a clue how to do that. I tried splitting them up and seeing if I could make it into tan(x/2) but I don't know.

Can anyone help on this? @SeanFM ?

(edited 7 years ago)

Reply 982

Marccs

Original post by SeanFM

Please link the paper. :h:

Hi
Can you help me with how they got this answer

in diff.JPG4.2KB

ln diff answeert.JPG20.2KB

Reply 983

Don Pedro K.

Original post by SeanFM

maybe it would help sketching both graphs so you can see it. I would translate 3 to the left and then stretch by 2.

Yeah haha I get it now, the 2, since it's a positive constant, can be outside or inside the mod. So |2(x+3)| = 2|(x+3)|, so you're right :smile:

Reply 984

gekkelekkebekke

Original post by ryandaniels2015

When solving trig equations do u have to show the cast or graph or can u calculate by 360-ans, etc etc

I just do sin(180-x), cos (360-x) and all 3 (sin, cos, tan) repeat with multiples of 360. just do a quick sketch to make sure you get all solutions. but in answer to your question, you don't NEED to if you feel confident using this way

Reply 985

ryandaniels2015

Thanks so much was stressing like mad!!!

Original post by MattWalton12

There isn't ever any method marks for the additional solutions, you find the first one and you can just write down all the others.

Reply 986

selenmer

Original post by Tow

How tf? Is this C3? I've not got a clue how to do that. I tried splitting them up and seeing if I could make it into tan(x/2) but I don't know.

Can anyone help on this? @SeanFM ?

I tried making 1 into sin^2x + cos^2x for the numerator and denominator and then factorising the sins and the coses if you get me but i have no idea......
Haha yes it is C3 sadly

Reply 987

badaman

Original post by ryandaniels2015

When solving trig equations do u have to show the cast or graph or can u calculate by 360-ans, etc etc

No need to show CAST.

Reply 988

Kevin De Bruyne

Original post by Marccs

Hi
Can you help me with how they got this answer

Nothing fancy.. with lnf(x), you find f'(x) * 1/f(x).

Reply 989

username1529975

Original post by selenmer

I tried making 1 into sin^2x + cos^2x for the numerator and denominator and then factorising the sins and the coses if you get me but i have no idea......
Haha yes it is C3 sadly

I even checked on a simplifying calculator and it can't simplify further. Where did you find this Q? It's not edexcel, I've done every past paper and never come across that!!

Reply 990

Frannoooooooo

Original post by Economistician

Does anyone know why this method doesn't work?

ln2x + ln(2x^2) + ln(2x^3) = 6
ln2x + 2ln2x + 3ln2x = 6
6ln2x = 6
ln2x = 1
e^ln2x = e^1
2x = e^1
x = (e^1)/2
?

It doesn't work because the powers apply only to x, and not to the whole term within the logarithm, so you can't just bring it down like you usually can. Someone else has already posted the method, but I think you could also separate the terms inside the logarithms which would allow you to bring down the powers for certain terms.

Reply 991

sjmacmen

How do you find the range and domain of functions?

Reply 992

Kevin De Bruyne

Original post by Tow

How tf? Is this C3? I've not got a clue how to do that. I tried splitting them up and seeing if I could make it into tan(x/2) but I don't know.

Can anyone help on this? @SeanFM ?

I can't see how to do it, sorry :redface:

Reply 993

ShatnersBassoon

Original post by Benji12345

What trig angles should we know? eg cos45=root2/2 or whatever etc?

sin30 = 1/2
sin45 = 1/root2 (or root2/2)
sin60 = root3/2
From there you can work out cos30, tan60, cosec45 etc.

You have a calculator so really all you need to learn is the numbers 'root2/2' and 'root3/2'. So, for instance if you needed to find the exact value of cos(pi/4), type it in your calculator and you'll get 0.07071... Then enter in your calculator root3/2 (0.8660...) and root2/2 (0.07071...) and you can easily see that cos(pi/4) = root2/2.

Reply 994

Jay_O

Original post by particlestudent

I think the thing with C4 is that what you have to do is very straightforward and you can think of the method right away, but because each question is so long, I just end up making mistakes everywhere :s-smilie:

.

I only need like 58UMS in each of these for an A overall, so this A* 90% rule is really annoying me :biggrin:

Yes spot on, i find C4 easier but cos of integration, methods can be very long leading to most likely mistakes being made.. But hopefully as you do more papers, accuracy improves greatly :smile:

yeah dw about that 90% thing, just focus on getting as close to 100% accuracy in every question you do, take each question one at a time and you'll be fine

Reply 995

username1529975

Original post by SeanFM

I can't see how to do it, sorry :redface:

Yeah I don't think this could come up. No application of rules or laws we learn in C3 works? Unless it wants you to differentiate or integrate to show otherwise. But aside from that, this cannot be simplified imo.

@selenmer

Reply 996

JP0458B

I'm so scared, stress doesn't even do it justice omg. I'm so scared because M2 was hard and I want to do well in C3 so badly but if they throw weird questions at me I know I'll panic 😓😭😲

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Reply 997

gekkelekkebekke

Original post by sjmacmen

How do you find the range and domain of functions?

domain will usually be given.. if not, depends on the graph, e^x has a domain of all real numbers but range of >0. try draw the graph. If you can't, the range might be bigger than the minimum, which you may need to find by differentiating and equating f'(x) to 0 and solving for the y value. look at the number of marks, if it is one mark, usually a straight forwards answer, like range of an inverse being the domain of the original function. If around 4, likely differentiation. 1/x-1 for example has the domain x (is not equal to) 0. if given a specific domain and a function, sub the x values of the domain and these will be your range values. hope this helps

Reply 998

Don Pedro K.

Original post by selenmer

Can anyone please help me do this trig proof? Thank you :smile:

Our only hope is @Zacken xD

Reply 999

WillRose

almost certain they took sketching arc functions and 1/(trig) fuctions out of the syllabus because of graphical calculators, unfair to people who dont have them