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    (Original post by Music With Rocks)
    In this question why is the angle not marked as 3\pi/4?

    Attachment 540463(apologies for rubbish quality)

    I am going to be keeping you guys busy with questions as I am basically self teaching FP2 having started on Friday you have been a great help so far
    Looks like an error.
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    (Original post by edothero)
    Looks like an error.
    Actually yeah their answer doesn't make sense at all as it is greater than pi...

    thank you, I don't trust myself enough to doubt the answers haha
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    And he's back again

    Name:  FP2 complex numbers q17.jpg
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    In part (e) what are the formulae used in calculating the area? I can't seem to find them in the textbook so assume they may be from one of the earlier modules and my memory isn't too great...
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    In polar coordinates, when finding area if you use limits of pi and 0 then times answer by 2 and get correct answer but the markscheme says to use limits of 2pi and 0, would you lose the marks?
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    (Original post by rm761)
    In polar coordinates, when finding area if you use limits of pi and 0 then times answer by 2 and get correct answer but the markscheme says to use limits of 2pi and 0, would you lose the marks?
    It's absolutely fine. You're just using symmetry.

    If you feel paranoid, just mention that you're using symmetry of the shape to get your answer.

    (Original post by Music With Rocks)
    And he's back again

    Name:  FP2 complex numbers q17.jpg
Views: 140
Size:  137.8 KB

    In part (e) what are the formulae used in calculating the area? I can't seem to find them in the textbook so assume they may be from one of the earlier modules and my memory isn't too great...
    Area of a circular sector = 1/2 x r^2 x theta? It's in radian measure in C2 if that helps jog your memory.
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    Please could anyone explain how to do question 19b and 19d here, really struggling with them! Thanks Name:  image.jpg
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    (Original post by economicss)
    Please could anyone explain how to do question 19b and 19d here, really struggling with them! Thanks Name:  image.jpg
Views: 257
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    I think for 19b you have to split it up into arg(z-2) - arg(z+i) = pi/4. As z represents any point, x+iy, then you know that if it lies on the negative real axis then y=0 so arg(x-2) = pi and arg(x+i) must therefore equal 3pi/4. Tan(3pi/4) = -1 so then you can work out the x coordinate from there with trig.

    With 13d, for part i, I think you can use the idea that the angle subtended at the centre of the circle from any two points on the circle is double the angle subtended at the circumference of the circle. For part ii, I'm not sure if there is a circle theorem you can use but you could show the arc length of A is 3/4 the circumference by working out the radius of the circle and the angle the arc moves through.
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    (Original post by PhysicsIP2016)
    I think for 19b you have to split it up into arg(z-2) - arg(z+i) = pi/4. As z represents any point, x+iy, then you know that if it lies on the negative real axis then y=0 so arg(x-2) = pi and arg(x+i) must therefore equal 3pi/4. Tan(3pi/4) = -1 so then you can work out the x coordinate from there with trig.

    With 13d, for part i, I think you can use the idea that the angle subtended at the centre of the circle from any two points on the circle is double the angle subtended at the circumference of the circle. For part ii, I'm not sure if there is a circle theorem you can use but you could show the arc length of A is 3/4 the circumference by working out the radius of the circle and the angle the arc moves through.
    Thanks so much, I'm probably missing the obvious but how does y=0 mean that arg (x-2)= pi please, sorry can't think of the link! Thanks
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    (Original post by economicss)
    Thanks so much, I'm probably missing the obvious but how does y=0 mean that arg (x-2)= pi please, sorry can't think of the link! Thanks
    As y=0, think of there being no imaginary component to the complex number. As x lies on the negative real axis, then x-2 can only be a negative real number, hence the argument of that must be pi
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    Is this another error in the solutionbank? Highlighted in red I am pretty sure the  i should be a  1 ?

    Name:  fp2 solution bank i.png
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    Or am I being dumb (I am prone to temporary lapses of maths ability)
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    (Original post by Music With Rocks)
    Is this another error in the solutionbank? Highlighted in red I am pretty sure the  i should be a  1 ?

    Name:  fp2 solution bank i.png
Views: 94
Size:  404.7 KB

    Or am I being dumb (I am prone to temporary lapses of maths ability)
    Correct. That is an error. However, it is rectified in the subsequent working.
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    (Original post by PhysicsIP2016)
    As y=0, think of there being no imaginary component to the complex number. As x lies on the negative real axis, then x-2 can only be a negative real number, hence the argument of that must be pi
    I see, thanks for your help Please could you draw a sketch for part di as I know the circle theorem you mean but I can't seem to draw it so that it helps me to find the answer! Thank you
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    (Original post by oinkk)
    Correct. That is an error. However, it is rectified in the subsequent working.
    oh I didn't spot that, thank you very much. Means I can actually do the question now as I know there is a correct answer

    (sorry I have rated you too recently to do it again )
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    HAVE I GONE MAD!?

    Name:  fp2 first order.png
Views: 141
Size:  190.8 KBFirst order differential question

    Please tell me this makes no sense because it certainly makes no sense to me. They seem to have the x terms flipped for no reason and pulled some t terms out of thin air.

    Could someone please check this for me to see if I still have my sanity
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    (Original post by Music With Rocks)
    HAVE I GONE MAD!?

    Name:  fp2 first order.png
Views: 141
Size:  190.8 KBFirst order differential question

    Please tell me this makes no sense because it certainly makes no sense to me. They seem to have the x terms flipped for no reason and pulled some t terms out of thin air.

    Could someone please check this for me to see if I still have my sanity
    Hmmm very strange indeed. Think I may be going mad aswell now -.-..

    If I had to guess I would say that it's not suppose to be dy/dx but dx/dt. That's probably where mistake is. If it were dy/dx then that would be a really easy differential equation to solve.
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    Thank you for all your help

    (Original post by Music With Rocks)
    HAVE I GONE MAD!?

    Name:  fp2 first order.png
Views: 141
Size:  190.8 KBFirst order differential question

    Please tell me this makes no sense because it certainly makes no sense to me. They seem to have the x terms flipped for no reason and pulled some t terms out of thin air.

    Could someone please check this for me to see if I still have my sanity
    Aha looks like another error to me :P
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    (Original post by Pyslocke)
    Hmmm very strange indeed. Think I may be going mad aswell now -.-..

    If I had to guess I would say that it's not suppose to be dy/dx but dx/dt. That's probably where mistake is. If it were dy/dx then that would be a really easy differential equation to solve.
    That would make it work actually, well spotted. It is pretty weird

    Thanks for looking at it and helping me keep a slight grip on sanity (sorry I can't rep you as I have done it too recently)

    (Original post by tripleseven)
    Aha looks like another error to me :P
    Edexcel should be paying me at this point for finding all these :rolleyes:
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    (Original post by economicss)
    I see, thanks for your help Please could you draw a sketch for part di as I know the circle theorem you mean but I can't seem to draw it so that it helps me to find the answer! Thank you
    I cannot seem to upload my picture for some reason but I have a major arc going through the coordinates (2,0) (0,2) (-1,0) and (0, -1) and then I've added a rough point of where the centre should be. I then drew 4 lines, one from (0, -1) to the centre, one from (0, -1) to the point (0,2), one from (2,0) to the centre and another one from (2,0) to the point (0,2). You can see the two angles subtended at the centre and the point (0,2).
    I am now trying to work on creating simultaneous equations from the diagram to calculate the coordinates of the centre, but hopefully you can see how it could work?
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    (Original post by economicss)
    Please could anyone explain how to do question 3c in here? Thanks Attachment 540083
    Hi what text book is this?
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    Could someone explain how to do part B to this question please. I always trip up on these simple 1 markers. Thanks.
    Name:  FP2.PNG
Views: 120
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