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# help with maths

rep for help

Original Poster

Need to find length BC and CD please?

Note: BE and CD are parallel

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

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.

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...

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