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    help with maths

    Hi can anyone help me answer the question in 1st reply?

    rep for help

    34 Comments

    Original Poster

    Need to find length BC and CD please?

    Note: BE and CD are parallel

    http://img127.imageshack.us/img127/2069/screenshot20100331at123.png

    Whats the question?

    Original Poster

    whatsThePoint;8252023

    Next letter is the sequence is F



    thanks :?

    are you doing Pythagoras or Trig?

    BC is half way of AC downwards an CD is the bottom line which goes across

    Original Poster

    emhaslam;8252051

    are you doing Pythagoras or Trig?



    I tried pythagoras but i thought i would need a 90 degree angle?

    BC is 6

    why not just draw it to scale on another bit of paper?

    CD is 16

    Banned

    emhaslam;8252102

    CD is 16



    answers are nothing without working out

    Original Poster

    emhaslam;8252077

    BC is 6



    emhaslam;8252102

    CD is 16



    how did you get this buddy?

    Working out - The smaller triangle is directly proportional to the bigger one. You can see that AD is two thirds bigger than AE, therefore BC needs to be two-thirds bigger than AB, and CD needs to be two-thirds bigger than BE.

    emhaslam;8252077

    BC is 6



    Incorrect 1 out of 10

    please try harder

    emhaslam;8252102

    CD is 16



    Incorrect again

    Detention next time. :-D

    scoff;8252128

    Incorrect 1 out of 10please try harder



    scoff;8252149

    Incorrect againDetention next time. :-D




    please explain! how i've done it seems right to me...

    BC 6 cd 25

    BC is Before Christ

    CD is Compact Disc

    HTH

    Original Poster

    emhaslam;8252124

    Working out - The smaller triangle is directly proportional to the bigger … Working out - The smaller triangle is directly proportional to the bigger one. You can see that AD is two thirds bigger than AE, therefore BC needs to be two-thirds bigger than AB, and CD needs to be two-thirds bigger than BE.



    best solution so far. does make sense i suppose :thumbsup: repped

    Hang about, you might be right... you might be wrong, dunno at the moment. lol

    using trig you can work out angle BAE and AEB, ADC will be the same as AEB.

    You then have 1 length and 2 angles of the large triangle, I am sure you can then work out the other sides from that (don't have anything to do it myself)

    i'm 99% sure i'm right... CD=16 BC=6

    it would be embarrassing if not - should be getting an A at A-Level in the summer...

    BC = 2/3 of AB =6 therefore AC =15
    A D =20 so 20 sq add 15 sq = 625 which the squzreroot is 25 therfore CD = 25

    Tanchi;8252081

    why not just draw it to scale on another bit of paper?



    I loved that, exactly what I'd have found myself doing in the middle of an exam! :oops:

    or AC squared + AD squared = CD squared. so square root of this is answer

    Original Poster

    the sedge;8252169

    BC 6 cd 25


    working out?
    greg_68;8252187

    using trig you can work out angle BAE and AEB, ADC will be the same as … using trig you can work out angle BAE and AEB, ADC will be the same as AEB.You then have 1 length and 2 angles of the large triangle, I am sure you can then work out the other sides from that (don't have anything to do it myself)


    I'll try this approach- thanks repped

    Original Poster

    the sedge;8252213

    BC = 2/3 of AB =6 therefore AC =15 A D =20 so 20 sq add 15 … BC = 2/3 of AB =6 therefore AC =15 A D =20 so 20 sq add 15 sq = 625 which the squzreroot is 25 therfore CD = 25



    the sedge;8252239

    or AC squared + AD squared = CD squared. so square root of this is … or AC squared + AD squared = CD squared. so square root of this is answer


    This is pythagoras but there is no 90 degree angle? :thinking:

    greg_68;8252187

    using trig you can work out angle BAE and AEB, ADC will be the same as … using trig you can work out angle BAE and AEB, ADC will be the same as AEB.You then have 1 length and 2 angles of the large triangle, I am sure you can then work out the other sides from that (don't have anything to do it myself)




    here may explain it easier given you know the above.

    use this to find the angles of the top triangle

    teacherschoice.com.au/mat…htm

    and this to find the angles / sides of the large one

    teacherschoice.com.au/Mat…gif

    Been a long long time since I had to do this, but heres how you solve it:


    * - Get ALL the angles of the top triangle (i.e. AB AE and BE)
    * - Now since BE and CD are parallel they are also the same angles as the bottom two angles of the top triangle (i.e. AEB = ADC and ABE = ACD).
    * - So you now have all the angles of the triangle and you can easily solve to find BC and CD.

    Heres the weblink:
    college-cram.com/stu…304
    Easy peasy.

    Can't do pythagoras as there is no 90 degree angle.
    I agree BC is 6cm as using ratios AE:ED is 12:8 = 3:2
    As the large triangle is a enlargement of the small triangle with a centre of enlargement A, the ratio of AB:BC will be the same, so 3:2 becomes 9:6
    Still using ratios AB:AC (also AE:AD and BE:CD) is 3:5 so 9.6 scales to 16cm as 9.6/3x5 is 16

    cattarn;8252344

    Can't do pythagoras as there is no 90 degree angle.I agree BC is 6cm as … Can't do pythagoras as there is no 90 degree angle.I agree BC is 6cm as using ratios AE:ED is 12:8 = 3:2As the large triangle is a enlargement of the small triangle with a centre of enlargement A, the ratio of AB:BC will be the same, so 3:2 becomes 9:6Still using ratios AB:AC (also AE:AD and BE:CD) is 3:5 so 9.6 scales to 16cm as 9.6/3x5 is 16



    well said.

    some people are over thinking this...

    just google it ;-)

    S=O/H C=A/H T=O/A


    SOHCAHTOA can't remember how you do it though....

    1.Angle B = D and E = D since they are parallel.
    2. Use Cosine Rule to find A,B,E
    3.Use Sine rule to find CD and Sine Rule for AC-9cm

    BC=6 CD=16

    its a ratio question. Didnt read the whole thread, but i think some people done it already
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