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    Hi, need some help with part B of my question. I've done part A no problem but can't do B, the way I usually do it by plugging in x=0 isn't working so can someone show me how they done it please! Thanks. I know it should be the easier part of the question but honestly hitting mind blanks with it now, appreciate any help
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    What actually went wrong when you tried x=0?
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    (Original post by bananagrimshaw)
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    Hi, need some help with part B of my question. I've done part A no problem but can't do B, the way I usually do it by plugging in x=0 isn't working so can someone show me how they done it please! Thanks. I know it should be the easier part of the question but honestly hitting mind blanks with it now, appreciate any help
    Plugging in x=0 should work, you get y=8\cos(\frac{\pi}{6}) and you can work out the value of cosine there by using a right-angled triangle or a calculator.
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    (Original post by RDKGames)
    Plugging in x=0 should work, you get y=8\cos(\frac{\pi}{6}) and you can work out the value of cosine there by using a right-angled triangle or a calculator.
    I know that pi/6 is 30° and that's root 3 over 2 but then I'm not sure how you get the answer of 4 root 3 or 6.93. I get 7.03 when I try to get a decimal answer and to get 4 root 3 from y= 8cos root 3 over 2, I'm assuming I devide the 8 by 2 but I've never been told that so I'm not sure, how would you do it? Thanks
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    (Original post by bananagrimshaw)
    I know that pi/6 is 30° and that's root 3 over 2 but then I'm not sure how you get the answer of 4 root 3 or 6.93. I get 7.03 when I try to get a decimal answer and to get 4 root 3 from y= 8cos root 3 over 2, I'm assuming I devide the 8 by 2 but I've never been told that so I'm not sure, how would you do it? Thanks
    Right I have no idea what is going on here with your working if I'm honest with you.

    Yes \frac{\pi}{6} radians is equivalent to 30 degrees. So \cos(\frac{\pi}{6})=\frac{\sqrt{  3}}{2} as you said yourself. Now to get 8\cos(\frac{\pi}{6}) you simply multiply both sides of \cos(\frac{\pi}{6})=\frac{\sqrt{  3}}{2} by 8 which gets you the 4\sqrt{3} as required.
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    (Original post by RDKGames)
    Right I have no idea what is going on here with your working if I'm honest with you.

    Yes \frac{\pi}{6} radians is equivalent to 30 degrees. So \cos(\frac{\pi}{6})=\frac{\sqrt{  3}}{2} as you said yourself. Now to get 8\cos(\frac{\pi}{6}) you simply multiply both sides of \cos(\frac{\pi}{6})=\frac{\sqrt{  3}}{2} by 8 which gets you the 4\sqrt{3} as required.
    Okay could you explain the last step, why do you times both sides by 8? I have never been told that and it explains why I've got stuck on this question. I'm sorry for being a pain! Really appreciate the help!!
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    (Original post by bananagrimshaw)
    Okay could you explain the last step, why do you times both sides by 8? I have never been told that and it explains why I've got stuck on this question. I'm sorry for being a pain! Really appreciate the help!!
    Because then you have 8\cos(\frac{\pi}{6}) on one side and its equivalent numerical value on the other which is what you want.
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    (Original post by RDKGames)
    Because then you have 8\cos(\frac{\pi}{6}) on one side and its equivalent numerical value on the other which is what you want.
    Okay thank you very much! I'm away to practice ones like this
 
 
 
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