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Edexcel A2 C3 Mathematics 12th June 2015

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I really dont get the questions where it says state maximum value of H(theta) for example with the trig stuff anyone?
Original post by 1 8 13 20 42
You want to find values such that (dh/dt) > 0. This means the rate of change is positive, hence an increase. So just find the critical value when dh/dt = 0 and you can work out the range of values from there


thanks
Original post by Sathya_James
The factor formulae where you have to make P+Q = A or something

Arccos arcsin arctan graphs too, have they ever come up?


I don't even know what the factor formula is, is it in the text book?


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Original post by s234590
I really dont get the questions where it says state maximum value of H(theta) for example with the trig stuff anyone?


I didn't until just recently, it's all to do with the relevant cos and sin graphs, it's hard to explain just do every question on exam solutions and I'll try help if you get stuck


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https://07a69ccf283966549a9350d1a66951a7bc96e2dc.googledrive.com/host/0B1ZiqBksUHNYZ0JQM1NRcmdHdXM/January%202014%20(IAL)%20QP%20-%20C3%20Edexcel.pdf
7b) ii
anyone got a clue?
Original post by Sathya_James
Have you already done c4 last year?

Yeah I'm a failure who is retaking A2.
Original post by gcsestuff
I didn't until just recently, it's all to do with the relevant cos and sin graphs, it's hard to explain just do every question on exam solutions and I'll try help if you get stuck
If you got Rcos(2theta +45) for example, the maximum occurs when cos(2theta +45)=1,so the maximum value would be R.

Posted fro
Original post by frozo123


rearrange for x and use cos^2(x) + sin^2(x) = 1
Original post by 1 8 13 20 42
rearrange for x and use cos^2(x) + sin^2(x) = 1


I used a triangle, what's your method?
how do you find a starting value for an iteration formula ?? from solomon a paper
Original post by frozo123


sin theta = x

cotx = cosx /sinx

root (1-sin^2) = cosx

rearrange for x
cotx = root (1-sin^2theta)/sin theta
and you know sin theta = x
Original post by frozo123
I used a triangle, what's your method?


The triangle is where that identity is derived from.
x = sintheta
cos^2(theta) = 1 - sin^2(theta)
costheta = root(1 - sin^2(theta)) = root(1 - x^2)

And then cot is cos/sin
Original post by 1 8 13 20 42
The triangle is where that identity is derived from.
x = sintheta
cos^2(theta) = 1 - sin^2(theta)
costheta = root(1 - sin^2(theta)) = root(1 - x^2)

And then cot is cos/sin


and also, when am I allowed to times and divide trig stuff?
Like in this example
3cosectheta + 8costheta=0
is it okay to times by sintheta?
Original post by frozo123
and also, when am I allowed to times and divide trig stuff?
Like in this example
3cosectheta + 8costheta=0
is it okay to times by sintheta?


Yeah. Multiplying usually isn't a problem, you just have to be wary of dividing in case of zero (I remember missing a solution in C2 due to that).
Original post by 1 8 13 20 42
Yeah. Multiplying usually isn't a problem, you just have to be wary of dividing in case of zero (I remember missing a solution in C2 due to that).


Yeah but when do you know when you can't divide? is it when it can factorise out?
If you got Rcos(2theta +45) for example, the maximum occurs when cos(2theta +45)=1,so the maximum value would be R.
Original post by gcsestuff
I didn't until just recently, it's all to do with the relevant cos and sin graphs, it's hard to explain just do every question on exam solutions and I'll try help if you get stuck


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Original post by frozo123
Yeah but when do you know when you can't divide? is it when it can factorise out?


Well you can divide, it's just if you're solving something equal to zero you need to remember that the common factor could equal zero. I can't think of a situation where you would need to divide unless it was to get rid of something that factorises out as you say, since usually we want to get rid of denominators.
ImageUploadedByStudent Room1433523141.107878.jpg

Can someone help me with this. I hate these questions:frown:

Ideally can I have a numerical method as I hate graphs


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Also; when doing questions like this

Can I always just do

Alpha= inversetan 2nd no./1st no

Thanks


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Original post by gcsestuff
I didn't until just recently, it's all to do with the relevant cos and sin graphs, it's hard to explain just do every question on exam solutions and I'll try help if you get stuck


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what bit is it under on exam solutions i cant find it

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