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lala2

help?!?

  • 10 months ago
  • 10 months ago

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  1. phi
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    what is angle B ?

    • 10 months ago
  2. phi
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    angle B= 180 - 24 can you find angle ACB knowing A is 16, and B is 156 ?

    • 10 months ago
  3. phi
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    remember 3 angles of a triangle add up to 180º

    • 10 months ago
  4. phi
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    if you can find angle ACB, you can use the Law of Sines to find the side BC \[ \frac{BC}{\sin 16}= \frac{7600}{\sin( ACB)} \]

    • 10 months ago
  5. phi
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    can you be more specific ?

    • 10 months ago
  6. phi
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    yes, angle at C is 8º now use the Law of Sines to find the length of side BC

    • 10 months ago
  7. lala2
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    bc/sin16= 7600/ sin (16)(156)(8)

    • 10 months ago
  8. phi
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    **im not typing i dont know why its saying that** that's scary. what is this bc/sin16= 7600/ sin (16)(156)(8) ?? \[ \frac{BC}{\sin 16}= \frac{7600}{\sin( 8º)} \]

    • 10 months ago
  9. lala2
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    hah! iknow

    • 10 months ago
  10. phi
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    no, I was trying to say the angle at C (start at A go to C, then go to B) the Law of Sines see http://www.mathsisfun.com/algebra/trig-sine-law.html uses the ratio of the sin(angle) / side opposite in this case, we want to know side BC, so we need to know the angle across from BC. we do , it is 16º we know side AB= 7600, so we want to know the angle opposite that side. it is angle C=8

    • 10 months ago
  11. phi
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    if you work it through, you can write \[ \frac{BC}{\sin (16º)}= \frac{7600}{\sin( 8º)} \] multiply both sides by sin(16). \[ \frac{BC}{\sin (16º) }\cdot \sin(16º)= \frac{7600}{\sin( 8º)} \cdot \sin(16º)\]

    • 10 months ago
  12. phi
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    on the left side, sin(16)/sin(16) "cancel" (become 1 so we can ignore) now get a calculator and figure out BC

    • 10 months ago
  13. phi
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    what were those 2's they are little º meaning "degrees"

    • 10 months ago
  14. phi
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    no. start with \[ \frac{BC}{\sin (16º) }\cdot \sin(16º)= \frac{7600}{\sin( 8º)} \cdot \sin(16º) \]

    • 10 months ago
  15. phi
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    only on the left side you should remember that anything divided by itself is 1 so the left side \[ \frac{BC}{\sin (16º) }\cdot \sin(16º) = BC \cdot \frac{\sin(16)}{\sin(16)}= BC \cdot 1 = BC \]

    • 10 months ago
  16. phi
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    you need a calculator to figure out the right side

    • 10 months ago
  17. phi
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    yes, but the sin(16) is up top 7600*sin(16)/sin(8)

    • 10 months ago
  18. phi
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    yes. but I think they want to the nearest foot

    • 10 months ago
  19. phi
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    you can use the Law of Sines to do part (b)

    • 10 months ago
  20. phi
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    in triangle BCD , what side do you know ?

    • 10 months ago
  21. phi
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    are you looking at the same picture I am ? put you finger on B, go to C, down to D, over to B. that triangle. which of its 3 sides do you know ?

    • 10 months ago
  22. phi
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    yes, but what did you figure out in part (a) ?

    • 10 months ago
  23. phi
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    You found the length of side BC in part (a) BC= 15052.07

    • 10 months ago
  24. lala2
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    oh!

    • 10 months ago
  25. phi
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    do you know the angle that is opposite to side BC ?

    • 10 months ago
  26. lala2
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    no.. how do i find that?

    • 10 months ago
  27. phi
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    the angle opposite side BC is the angle that is not B and not C

    • 10 months ago
  28. lala2
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    im sorry but i just dont understand..

    • 10 months ago
  29. phi
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    what is the *angle* opposite side BC ? you have 3 choices: B , C or D. (and it's not B or C)

    • 10 months ago
  30. phi
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    |dw:1369784436661:dw|

    • 10 months ago
  31. lala2
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    i thought you meant side not angle

    • 10 months ago
  32. phi
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    that means we can write down \[ \frac{15052.07}{\sin(90)} = \] now you need a side (I would pick the one we are looking for, and its opposite angle)

    • 10 months ago
  33. lala2
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    right?

    • 10 months ago
  34. phi
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    yes, write CD over sin(24) and set that equal to the first ratio (up above) what do you get ?

    • 10 months ago
  35. phi
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    I don't know what that is. You should be writing down the equation that you get when you use the Law of Sines. In part (a) we used \[ \frac{BC}{\sin (16)}= \frac{7600}{\sin( 8)} \] your job is to write a similar equation for part (b) you already have both sides....

    • 10 months ago
  36. phi
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    *both sides of the equation \[ \frac{15052.07}{\sin(90)} = \] and ....

    • 10 months ago
  37. phi
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    yes, but use that in the equation... CD/sin(24) is part of the equation

    • 10 months ago
  38. phi
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    the idea is length/sin(angle) = length/ sin(angle)

    • 10 months ago
  39. phi
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    perfect. now "solve" for CD multiply both sides by sin(24) (this will "cancel" sin(24) on the right side)

    • 10 months ago
  40. phi
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    that is the right side of the equation. you should also show the other side. in other words, start with \[ \frac{15052.07}{\sin(90)} = \frac{CD}{\sin(24)} \] multiply both sides by sin(24). the right side will simplify to CD, just like you showed what do you get for the left side of the equation ?

    • 10 months ago
  41. phi
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    not after you multiply it by sin(24)

    • 10 months ago
  42. phi
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    \[ \frac{15052.07}{\sin(90)} = \frac{CD}{\sin(24)} \\ \frac{15052.07}{\sin(90)} \cdot \sin(24)= \frac{CD}{\sin(24)}\cdot \sin(24) \\\frac{15052.07}{\sin(90)} \cdot \sin(24)= CD \]

    • 10 months ago
  43. phi
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    now round to the nearest foot. that is the answer for part (b)

    • 10 months ago
  44. phi
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    This was a difficult problem. But it go faster if you try to learn some of this.

    • 10 months ago
  45. lala2
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    Thank you @phi! I really apperciate your help and patience

    • 10 months ago
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