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Size:  360.5 KB hi, I am a bit stuck on part b and c of this question. To solve this, apparently line Ad is perpendicular to l1 but how can that be as the angle in between isn't a right angle. I know that l1 and l2 are parallel and the other two lines are as well. Thanks.
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    I need someone to explain why AD would be perpendicular to l1... Thanks in advance.
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    It's a parrallelogram so It can't be a right angle
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    (Original post by lytran)
    It's a parrallelogram so It can't be a right angle
    ...I, say what? A rectangle is a parallelogram... what are the angles in a rectangle?
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    (Original post by Zacken)
    ...I, say what? A rectangle is a parallelogram... what are the angles in a rectangle?
    But in that question , it didnt say a rectangle so i just assume that it's just this one
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    (Original post by coconut64)
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Size:  360.5 KB hi, I am a bit stuck on part b and c of this question. To solve this, apparently line Ad is perpendicular to l1 but how can that be as the angle in between isn't a right angle. I know that l1 and l2 are parallel and the other two lines are as well. Thanks.
    In answer to your question, AD is not perpendicular to \ell_1, either you are reading wrong or the markscheme is wrong. What I suspect is happening is that you are reading wrong and that the mark scheme is finding a line that passes through A and is perpendicular to \ell_1 but this does not imply that the line also passes through D.
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    (Original post by Zacken)
    In answer to your question, AD is not perpendicular to \ell_1, either you are reading wrong or the markscheme is wrong. What I suspect is happening is that you are reading wrong and that the mark scheme is finding a line that passes through A and is perpendicular to \ell_1 but this does not imply that the line also passes through D.
    Yeah , sorry my mistake. I got confused that's why. So this is what I think is happening: find the perpendicular line to L1 going through A. Then find the point of intersection with L2. Then work out the distance between A and the point of intersection? Right?
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    (Original post by coconut64)
    Yeah , sorry my mistake. I got confused that's why. So this is what I think is happening: find the perpendicular line to L1 going through A. Then find the point of intersection with L2. Then work out the distance between A and the point of intersection? Right?
    Yes.
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    (Original post by Zacken)
    Yes.
    Great. So this distance is the same as the length of AD/ bc ? Because for part c, they used length of AB and the distance found in the previous part of the question.
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    (Original post by coconut64)
    So this distance is the same as the length of AD/ bc ? Because for part c, they used length of AB and the distance found in the previous part of the question.
    Well... no - look up the definition of an area of a parallelogram, it's the side * perpendicular height. Not side * side. You can find the length AB and you've just found the perpendicular height, not AD.
 
 
 
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