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    This is a topic covered in Edexcel Mathematics but im struggling to understand the concept and is confusing :/
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    (Original post by ChocoholicCox)
    This is a topic covered in Edexcel Mathematics but im struggling to understand the concept and is confusing :/
    If you have a specific question you're struggling it would make it easier for people to assist you.
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    Name:  Trigonometry.jpg
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Size:  5.7 KB This is a question which I have been given I know that for some these you have to do pythagrous aswell
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    (Original post by ChocoholicCox)
    Name:  Trigonometry.jpg
Views: 100
Size:  5.7 KB This is a question which I have been given I know that for some these you have to do pythagrous aswell
    What do you need to find?
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    (Original post by ChocoholicCox)
    Name:  Trigonometry.jpg
Views: 100
Size:  5.7 KB This is a question which I have been given I know that for some these you have to do pythagrous aswell
    OK, here's one way of thinking about it.

    First a general point. Almost all, if not all, the 3D problems that you're going to encounter at A-level, can be looked at in terms of 2D. The only difference is that the planes you're considering may not be horizontal or vertical, but lie at an angle.

    Since they're really only 2D, then all the geometry you've learnt dealing with flat shapes applies: Pythagoras, sine rule, cosine rule, opposite angles are equal, etc.

    The issue is firstly identify what are the relevant planes.

    So, lets look at the length y. Well it's the diagonal of the rectangle EFGH. We know what the sides of the rectangle are, because this is a cuboid - all the faces of the overall shape are at 90 degrees to each other.

    The angle GFH is easy (if you're required to work that out, it's not clear from the diagram) - it lies in the same plane as that rectangle.

    Now what about x. It refers to a line. We need to consider another point in addition to get a plane. So lets choose F as a fairly obvious one.
    Our plane contains the triangle CFH. We know it's a right-angled triangle, as CF is vertical and FH horizontal. We also know the lengths of CF and FH now.

    Hope that helps.
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