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    Anyone good at maths?

    I have got a really hard question in one of my assignments, and i originally failed this question in september and i got it back to re-do and i still cant do it! If anyone can help me i would be really grateful.

    The question goes as follows:

    In the diagram below (Fig 1)AB is the inclined jib of a crane and is 10m long. AC is 4m long. Using the sine rule, calculate the inclination of the jib to the vertical and the length of tie CB. "

    The picture is here: img36.imageshack.us/img…png

    24 Comments

    i was hoping it was going to be 8+6 !?!?!?

    sine is equal to opposite / hypotopomus

    Original Poster

    haha i wish it was as easy as that foxy!

    ctuk;5524114

    sine is equal to opposite / hypotopomus



    thougth that only applied to a right angled triangle.

    what does the "120" refer to in the picture?

    Banned

    If the 120 is the angle then maybe it is 120/10 * 4

    Original Poster

    120 is an angle so 120 degrees

    Banned

    Silly Old Hitler Couldn't Advance His Troops Over Asia

    Sin= O/H, Cos= A/H, Tan= O/A

    Banned

    Paddy Charlie;5524212

    Silly Old Hitler Couldn't Advance His Troops Over AsiaSin= O/H, Cos= A/H, … Silly Old Hitler Couldn't Advance His Troops Over AsiaSin= O/H, Cos= A/H, Tan= O/A



    I dont think you can use that hear. That is trigonometry and this requires SINE rule. I think the formula is A/a=B/b=C/c

    kiwinator;5524198

    120 is an angle so 120 degrees



    the angle BCA = 120 degs?

    a2 + b2 = c2
    a2 = 16 b2 = 100 c2 = 116

    sooo length CB must be = 10.770329614269007 ???

    Here is the sine rule

    http://www.ucl.ac.uk/mathematics/geomath/trignb/sin2.gif

    http://www.ucl.ac.uk/mathematics/geomath/trignb/sin1.gif

    ctuk;5524268

    a2 + b2 = c2 a2 = 16 b2 = 100 c2 = 116sooo length CB must be = … a2 + b2 = c2 a2 = 16 b2 = 100 c2 = 116sooo length CB must be = 10.770329614269007 ???



    If BCA is 120 degrees then CB will be shorter than AB

    I'm beginning to think there maybe some info missing here

    the lines CB=a, AB=c and AC=b

    So the first bit you wanna find A

    use c/sinC = b/sinB
    10/sin120 = 4/sinB
    rearrange for sinB, then find B

    As you know A+B+C=180, you can find A

    Now you have found A you can use c/sinC = a/SinA, where a is you're line CB

    BCA isnt 120, BC-upwards is 120 ? i think

    so BCA must be 60

    Banned

    tr2k8;5524229

    I dont think you can use that hear. That is trigonometry and this … I dont think you can use that hear. That is trigonometry and this requires SINE rule. I think the formula is A/a=B/b=C/c



    Ah, I can't seen the diagram here in work so can't help then

    mug51;5524330

    the lines CB=a, AB=c and AC=bSo the first bit you wanna find Ause c/sinC … the lines CB=a, AB=c and AC=bSo the first bit you wanna find Ause c/sinC = b/sinB10/sin120 = 4/sinBrearrange for sinB, then find BAs you know A+B+C=180, you can find ANow you have found A you can use c/sinC = a/SinA, where a is you're line CB



    Mug51 has it but you need a scientific calculator which i dont posess at work

    probs one online though

    I drew it out based on the details & got BC = 7.5m
    angle at c = 120, b = 20 & a = 40
    probably wrong :whistling:

    i get B to be 20.26790106 degrees, so A = 39.73209894

    and CB to be 7.380831519

    mr.potato_head;5524399

    Mug51 has it but you need a scientific calculator which i dont posess at … Mug51 has it but you need a scientific calculator which i dont posess at work



    Windows Calculator does it. Open it, then in the menu at the top, View > Scientific

    J9STL;5524436

    I drew it out based on the details & got BC = 7.5mangle at c = 120, b = … I drew it out based on the details & got BC = 7.5mangle at c = 120, b = 20 & a = 40 probably wrong :whistling:


    lol look at the answers i got, you pretty much got my answers

    mug51;5524450

    i get B to be 20.26790106 degrees, so A = 39.73209894and CB to be … i get B to be 20.26790106 degrees, so A = 39.73209894and CB to be 7.380831519



    Along those lines I get it to be 39.76 degrees and 7.39 m

    Original Poster

    Thanks for all your help guys, im gonna try and go through all the help in more detail soon
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