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Mimi_x3

  • 4 years ago

Cindy is some distance NW from a building Don is some distance due North of a building. If Don is twice as far as Cindy from the building and they are 40m apart, calculate their distances to the building to the nearest one-tenth of metre. Can someone please explain step by step on how to do this, I'm like so lost

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  1. xactxx
    • 4 years ago
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    Okay. |dw:1316163703925:dw|

  2. Mimi_x3
    • 4 years ago
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    Do i calculate x by soh cah toa thing ?

  3. xactxx
    • 4 years ago
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    no, the triangle is not guaranteed to be right angled.

  4. xactxx
    • 4 years ago
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    do you know of the sine rule?

  5. Mimi_x3
    • 4 years ago
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    Yup, do i use the sine rule ?

  6. MeEngr
    • 4 years ago
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    use law of cosines or law of sines here to find the angles from the lengths

  7. xactxx
    • 4 years ago
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    you can use cosine rule a^2 = b^2+c^2-2bc cos A for angle B

  8. xactxx
    • 4 years ago
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    you'll get x that way

  9. Mimi_x3
    • 4 years ago
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    Okay, like 40/sin45 = x/sinC ?

  10. Mimi_x3
    • 4 years ago
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    w8 nvm

  11. xactxx
    • 4 years ago
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    40^2 = x^2 + (2x)^2 - 2x(2x) cos 45 1600 = x^2 + 4x^2 - 4x^2 (1/sqrt(2)) 1600 = 5x^2 - 2sqrt(2)x^2 1600 / (5 - 2sqrt(2)) = x^2 x^2 = 736.79 x = sqrt(736.79) = 27.14m So Don is 27.1*2 = 54.2m away from the building and Cindy is 27.1m away from the building.

  12. Mimi_x3
    • 4 years ago
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    Tyvm (:

  13. xactxx
    • 4 years ago
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    btw in the diagram I swapped Cindy and Don, but that's not too much of a problem... the problem works itself out in the same way.

  14. Mimi_x3
    • 4 years ago
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    Okay xD

  15. Mimi_x3
    • 4 years ago
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    Um , I did it and I got x= 47.568 xD

  16. xactxx
    • 4 years ago
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    I still you should still get to the same answer...?

  17. Mimi_x3
    • 4 years ago
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    idk, thats how i did it 1600 = x^2 + 4x^2 - 4x^2 * cos45 1600 = x^2 *cos45 cos45x^2 = 1600 x^2 = 2262.74 x = 47.578 Did I stuff it up somewhere ?

  18. xactxx
    • 4 years ago
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    yes. You first perform multiplication, then subtraction, according to BODMAS. You first applied subtraction and then multiplication!

  19. Mimi_x3
    • 4 years ago
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    Hm, i don't follow the BODMAS thing xD Wonder why I stuffed it up xD but how did I stuff it up ? Since I already subtracted it first

  20. xactxx
    • 4 years ago
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    1600 = x^2 + 4x^2 - 4x^2 * cos 45 You first performed addition and subtraction: 1600 = x^2 * cos 45 when you should have first performed multiplication! 1600 = x^2 + 4x^2 - 2.828x^2

  21. Mimi_x3
    • 4 years ago
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    Where did you get 2.828 from ?

  22. xactxx
    • 4 years ago
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    4 * cos 45

  23. Mimi_x3
    • 4 years ago
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    Oh yeah my bad i forgot about that Thank you (:

  24. xactxx
    • 4 years ago
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    Sure.

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