Edexcel Core 3 - 21st June 2016 AM

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

Sketch

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

showing all intersections

ln((1/2)e^2) = ln(1/2) + ln(e^2) = ln(2^(-1)) + 2 = -ln2 + 2 = 2 - ln2

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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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.

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.

for modulus questions how would you know if theres two solutions without drawing the graph

I'm doing question 5 on this and I'm not getting the right answer

http://www.madasmaths.com/archive/iygb_practice_papers/c3_practice_papers/c3_x.pdf


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was the answer to the question (2-ln2, 4). I dont wanna check lol in case i ruin the solution

Is an inflection point the same as a turning point???

Inflection points are special turning points. They are neither maxima nor minima.

Like (0,0) on y=x^3?

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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