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    http://prntscr.com/avi1we

    Can anyone explain to me how to do this thanks
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    (Original post by junayd1998)
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    Can anyone explain to me how to do this thanks
    Let angle CPB = x. Then what is angle COB in terms of x?
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    (Original post by junayd1998)
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    Can anyone explain to me how to do this thanks
    You know that angles in a quadrilateral add up to 360. You have three of the angles. The fourth angle is then COB.

    So you know that COB + 90 + 90 + BPC = 360, so: COB = 180 - BPC.

    Then you know that AOB + COB has to add up to 180 since it's a straight line.
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    Since its gcse its probably ok just to chose an angle for COB to be so then you can work up from that

    https://gyazo.com/22cb03d7ea76b62dc3208611ee605122

    sum of interior angles of a quad = 360
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    (Original post by SalazarSlytherin)
    Since its gcse its probably ok just to chose an angle for COB to be so then you can work up from that

    https://gyazo.com/22cb03d7ea76b62dc3208611ee605122

    sum of interior angles of a quad = 360
    It may only be GCSE but you'd still get zero marks for that.

    You haven't proved it for all angles.
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    (Original post by SalazarSlytherin)
    Since its gcse its probably ok just to chose an angle for COB to be so then you can work up from that

    https://gyazo.com/22cb03d7ea76b62dc3208611ee605122

    sum of interior angles of a quad = 360
    So just choose any number for COB and work around that?
    Idk tho it says you have to give reasons at each stage.
    To be honest, for me that is probably the most easier way to do.
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    (Original post by junayd1998)
    So just choose any number for COB and work around that?
    Idk tho it says you have to give reasons at each stage.
    To be honest, for me that is probably the most easier way to do.
    Yeah but cause you can see COB is more than 90 degrees, use a realistic angle.
    The reasons would just be quad angles = 360, straight line = 180, circle = 360
    (Original post by notnek)
    It may only be GCSE but you'd still get zero marks for that.

    You haven't proved it for all angles.
    Ok then one sec while I prove it for angle COB = 1, COB = k and COB = k+1

    /s
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    (Original post by SalazarSlytherin)

    Ok then one sec while I prove it for angle COB = 1, COB = k and COB = k+1
    ...I don't think you understand how a proof works. That would prove it for just the set of naturals. COB is real-valued.
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    (Original post by junayd1998)
    So just choose any number for COB and work around that?
    Idk tho it says you have to give reasons at each stage.
    To be honest, for me that is probably the most easier way to do.
    In case you didn't read my previous post, you would get no marks in an exam for choosing numbers in a proof question.
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    (Original post by notnek)
    In case you didn't read my previous post, you would get no marks in an exam for choosing numbers in a proof question.
    Okay so lets say COB is X we got our two 90 angles how do we figure out CPB?

    X+90+90+CPB=360
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    (Original post by junayd1998)
    Okay so lets say COB is X we got our two 90 angles how do we figure out CPB?

    X+90+90+CPB=360
    Why would you want to figure out CPB?

    You know that x + 90 + 90 + CPB = 360

    And you also know that AOB + x = 180
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    Think about the angles CPB and AOB in terms of the other angles, making an equation for each angle. There is a quadrilateral OBCP, so think about internal angles in a quadrilateral. You should end up with CPB = AOB

    Reasons for each step can be expressed in a few words, such as "Angles on a straight line equal 180 degrees." They do not need to be too detailed, or proven using values of angles, as you are not given any values of angles. Apart from the two right angles you have labelled, no other angle can be given an accurate value.
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    Who is doing the higher tier paper, OCR this year ??
 
 
 
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