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# Edexcel Core 3 - 21st June 2016 AM watch

1. for modulus questions how would you know if theres two solutions without drawing the graph
2. (Original post by penguin234)
Hi, would anyone be able to explain June 2015 q3 part c to me pls?? I can do parts a and b. I think there was a question like this in the June 2013 R paper as well which was also q3 part c. The 2015 question is this:

g(ș) = 4cos2ș + 2sin2ș
Given that g(ș) = R cos(2ș+alpha), where R> 0 and 0 < alpha < 90°,
(a) find the exact value of R and the value of alpha to 2 decimal places.(3)
(b) Hence solve, for –90° < ș< 90°,4cos2ș + 2sin2ș = 1, giving your answers to one decimal place.

Given that k is a constant and the equation g(ș) = k has no solutions,
(c) state the range of possible values of k.
So k/r cannot be greater than 1 or less than -1 because cos and sin range is between -1 and 1.

So k cannot be greater than r or less then -r, therefore r > k > -r

Edit: misread the question, what i wrote was for k to have solutions.

For k to have no solutions k/r has to be greater than 1 or less than -1, so k> 1 or k< -1
3. (Original post by metrize)
So k/r cannot be greater than 1 or less than -1 because cos and sin range is between -1 and 1.

So k cannot be greater than r or less then -r, therefore r > k > -r

Edit: misread the question, what i wrote was for k to have solutions.

For k to have no solutions k/r has to be greater than 1 or less than -1, so k> 1 or k< -1
Oh yeah, that makes so much sense!! Thank you so much!!!
4. (Original post by Pablo Picasso)
Sketch

y = x^2 + 5|x| - 3
y = x^2 + |5x - 3|

showing all intersections
How do you do this one? y = x^2 + |5x - 3|
5. (Original post by 13 1 20 8 42)
ln((1/2)e^2) = ln(1/2) + ln(e^2) = ln(2^(-1)) + 2 = -ln2 + 2 = 2 - ln2
Thanks, had a bit of a dense moment

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6. (Original post by Don Joiner)
On iterations questions when you select intervals to show that there is a sign change.. Is it okay to leave your answer in standard form? As the answer you get is almost always very small

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Yes, the important part is the sign

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7. (Original post by Glavien)
How do you do this one? y = x^2 + |5x - 3|
sketch the curve for x >= 3/5 which would be y = x^2 + 5x - 3, and then sketch the curve for x < 3/5 which would be x^2 -5x + 3. The curve is continuous and should have a cusp at x = 3/5.
8. (Original post by AMarques)
sketch the curve for x >= 3/5 which would be y = x^2 + 5x - 3, and then sketch the curve for x < 3/5 which would be x^2 -5x + 3. The curve is continuous and should have a cusp at x = 3/5.
Yes
9. (Original post by chickenhips223)
Order food from UBER using code: uberfood16 to get £10 off your first delivery.They don't charge for the actual delivery btw!! and there is no minimum charge.
lol
10. (Original post by imran_)
for modulus questions how would you know if theres two solutions without drawing the graph
You're better off not risking it and drawing a graph to make it far more easier for you.
11. (Original post by pineneedles)
I'm doing question 5 on this and I'm not getting the right answer

Attachment 553022
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was the answer to the question (2-ln2, 4). I dont wanna check lol in case i ruin the solution
12. (Original post by bat_man)
was the answer to the question (2-ln2, 4). I dont wanna check lol in case i ruin the solution

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13. Is an inflection point the same as a turning point???
14. (Original post by Engineerrookie)
Is an inflection point the same as a turning point???
Inflection points are special turning points. They are neither maxima nor minima.
15. (Original post by 13 1 20 8 42)
Inflection points are special turning points. They are neither maxima nor minima.
Like (0,0) on y=x^3?
16. (Original post by Craig1998)
Like (0,0) on y=x^3?
Exactly
edit: Hmm it seems from formal definition that they aren't necessarily stationary points, merely where curvature changes (this means that the second derivative must be zero - so it just requires that the first derivative is constant) However I think at a level you will only care about inflection points which are also stationary, if any at all
17. I keep getting about 86-89 UMS in papers and keep losing marks from the domain range questions and also silly mistakes, can I get 90UMS on Tuesday??

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18. (Original post by Don Joiner)
I keep getting about 86-89 UMS in papers and keep losing marks from the domain range questions and also silly mistakes, can I get 90UMS on Tuesday??

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I guess it depends if a range/domain question comes up then...
19. hey does anyone have the C34 jan 2016 international paper? sorry if it was already posted!
20. Do you think if I get 69 out of 75 on both C3 and C4 I could get an A*???

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