Edexcel A2 C3 Mathematics 12th June 2015

I don't get the final question on C3 june 2014, I thought the minimum value on a sin graph is -1 which occurs at 3/2pi? Surely if the minimum value is -1, and you are stretching it by 100 then adding 4 the minimum becomes -96?!

Whoops my question was too hard for edexcel students never mind.


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With the binomial shown in my notes, which validity would I choose? Because you work out the validity of both expansions but overall have to choose one, how do I work out which one it is?


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The sine function inside the brackets has been squared in the question, which means H(ϑ) cannot be negative. Therefore, the smallest value it could be would be 0, since all the negative values would become positives.

Then you equate H(ϑ) = 0, and solve normally.

regardless of the fact that this is a C3 thread; for that validity question, you're meant to chose the value that satisfies both of the equations/statements/validity binomial equations.

In short, your answer would be: (1+4x) ^ -1.


this is because, the modulus 'x' value in that equation is 0.25; which is less than the other modulus 'x' value (which is: 0.3) and as such, it satisfies both equations.


if you're still confused:
the (1+4x) ^ -1 equation has: *'modulus x modulus' = 1/4*. this means that it has a numerical x value (on an x-axis in a graph) that starts from: -0.25 to 0.25.


the other one, the (1+3x) ^ -1 equation has: *'modulus x modulus' = 1/3*. this means that it has a numerical x value (on an x-axis in a graph) that goes from: -0.33 to 0.33.


therefore i say go for the (1+4x) ^ -1, as that value goes from -0.25 to 0.25. that is, these are x values that would appear in both x-axis ranges. you wouldn't choose the other equation as,

is that clear or have i made a complete fool of myself either with the working out or with the explanation? :P

Cause it's a c4 question this is a c3 thread


Posted from TSR Mobile

The sine function inside the brackets has been squared in the question, which means H(ϑ) cannot be negative. Therefore, the smallest value it could be would be 0, since all the negative values would become positives.

Then you equate H(ϑ) = 0, and solve normally.

you my sir, are a genius. my entire class (teacher included); spent about 20-30 mins on this particular question; and to this day, are unsure about an exact way of solving it other than praying to God that it doesn't come up in the exams; and committing Japanese samurai ritual if it does.


thank you So much..

seriously? you guys need a new teacher haha

help 5c

You know what your A value has to be. Can you choose a suitable b, bearing in mind what they've asked in the question?

ive done cos(60+15)/sin(60+15) but get the wrong answer

I don't think you can have cos on top - it doesn't look like you've used part b.

You know on the LHS of the equation you need A = 75, because whatever B is, on the RHS you will have cotA, which is cot75.

Now you just need a suitable value for b, so that some of the terms like cos(A-B) and sin(A-B) = cos60 and sin60 respectively...

you my sir, are a genius. my entire class (teacher included); spent about 20-30 mins on this particular question; and to this day, are unsure about an exact way of solving it other than praying to God that it doesn't come up in the exams; and committing Japanese samurai ritual if it does.


thank you So much..

Bloody marvelous! Makes sense, cheers

20 minutes haha really?
And btw my previous comment should have said 'H(ϑ) = 4 then solve normally'

no worries

no joke.. i still remember the white board screen as we all tried to make sense of the disgusting question; and the repulsive, depressed feeling one gets when they (& the whole damn class) can't do a question.