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    (Original post by ThePersian)
    Oh, Okay thanks
    No worries
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    (Original post by hello.cupcake)
    Sorry to be a pain but I can't do probability!!!!!!

    For question 6c, why don't you include the outside of the Venn Diagram when finding the probability of A and not B? Surely the outside counts as the not B bit?

    Thanks you're all amazing, bye.
    They're asking for the probability of A given that B doesn't happen. The outside does count as "not B", though.
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    Hmm, stuck on a log question:

    Solve for x:

     5^{x} = 3^{x-1}

    So far, I have:

     xlog5 = xlog3 - log3

    but I have no idea where to go from there :confused:. Help?
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    (Original post by Choppie)
    Hmm, stuck on a log question:

    Solve for x:

     5^{x} = 3^{x-1}

    So far, I have:

     xlog5 = xlog3 - log3

    but I have no idea where to go from there :confused:. Help?
    Rearrange then factor out the x
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    Today has gone pretty well - S in STEP III mock, as well as 75/75 in C4 mock.
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    (Original post by joostan)
    Rearrange then factor out the x
    How could I have not spotted that?! Thanks!
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    (Original post by Choppie)
    How could I have not spotted that?! Thanks!
    Any time
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    Can anyone help me with this question please...

    Show that cotx - sin2x = cotxcos2x for 0<x<180 (3 marks)


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    (Original post by annaridgway95)
    Can anyone help me with this question please...

    Show that cotx - sin2x = cotxcos2x for 0<x<180 (3 marks)


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    Is this a show that or a solve for x?

    First off rewrite cot(x) in terms of sin and cos, then write the LHS as one fraction
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    (Original post by joostan)
    Is this a show that or a solve for x?

    First off rewrite cot(x) in terms of sin and cos, then write the LHS as one fraction
    First part is show that, second part asks to solve... Do I need to change sin2x into 2sinxcosx?


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    (Original post by annaridgway95)
    First part is show that, second part asks to solve... Do I need to change sin2x into 2sinxcosx?


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    Yep:
    So you've got:
    \frac{\cos(x)}{\sin(x)} - 2\sin(x)\cos(x)
    What now?
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    (Original post by joostan)
    Yep:
    So you've got:
    \frac{\cos(x)}{\sin(x)} - 2\sin(x)\cos(x)
    What now?
    I'm so confused :/ I've got up to that bit


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    • Study Helper
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    Study Helper
    (Original post by DJMayes)
    Today has gone pretty well - S in STEP III mock, as well as 75/75 in C4 mock.
    Congratulations, that's brilliant! I just did my unit 1 Chemistry mock and its like reliving my experience last year :-/ Also I think I've planned to do a STEP I mock tomorrow so i hope it goes well, although I need to get the video of all the teachers dancing to gangnam style for the leavers assembly, it's going to be hilarious!


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    (Original post by annaridgway95)
    I'm so confused :/ I've got up to that bit


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    Rewrite as:
    \dfrac{\cos(x)- 2\sin^2(x)\cos(x)}{\sin(x)}
    Can you see what I did here, and what the next step is?
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    (Original post by joostan)
    Rewrite as:
    \dfrac{\cos(x)- 2\sin^2(x)\cos(x)}{\sin(x)}
    Can you see what I did here, and what the next step is?
    Yeah that makes sense, still don't know what to do next though D: change 2sin^2x into 2(1-cos^2x) ? I really don't know..


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    (Original post by annaridgway95)
    Yeah that makes sense, still don't know what to do next though D: change 2sin^2x into 2(1-cos^2x) ? I really don't know..
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    Consider a double angle expression for cos(2x) . . .
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    (Original post by joostan)
    Consider a double angle expression for cos(2x) . . .
    There's only a cos2x on the RHS though isn't there?


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    (Original post by annaridgway95)
    There's only a cos2x on the RHS though isn't there?


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    \cos(2x)= \cos^2(x) - \sin^2(x) = (1 -\sin^2(x)) - sin^2(x)
    You can finish up
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    (Original post by joostan)
    \cos(2x)= \cos^2(x) - \sin^2(x) = (1 -\sin^2(x)) - sin^2(x)
    You can finish up
    1 - 2sin^2x but I don't understand where that fits in?


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    (Original post by annaridgway95)
    1 - 2sin^2x but I don't understand where that fits in?


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    Never mind, I'm being stupid! Hahaha.
    Thank you!


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