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Anyone good at maths?

kiwinator Avatar
7y, 5m agoPosted 7 years, 5 months ago
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: http://img36.imageshack.us/img36/916/mathsquestion.png
kiwinator Avatar
7y, 5m agoPosted 7 years, 5 months ago
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(24) Jump to unreadPost a comment
Comments/page:
#1
:o i was hoping it was going to be 8+6 !?!?!?
#2
sine is equal to opposite / hypotopomus
#3
haha i wish it was as easy as that foxy!
#4
ctuk
sine is equal to opposite / hypotopomus


thougth that only applied to a right angled triangle.
#5
what does the "120" refer to in the picture?
banned#6
If the 120 is the angle then maybe it is 120/10 * 4
#7
120 is an angle so 120 degrees
banned#8
Silly Old Hitler Couldn't Advance His Troops Over Asia

Sin= O/H, Cos= A/H, Tan= O/A
banned#9
Paddy Charlie
Silly Old Hitler Couldn't Advance His Troops Over Asia

Sin= 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
#10
kiwinator
120 is an angle so 120 degrees


the angle BCA = 120 degs?
#11
a2 + b2 = c2
a2 = 16 b2 = 100 c2 = 116

sooo length CB must be = 10.770329614269007 ???
#12
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
#13
ctuk
a2 + b2 = c2
a2 = 16 b2 = 100 c2 = 116

sooo 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
#14
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
#15
BCA isnt 120, BC-upwards is 120 ? i think

so BCA must be 60
banned#16
tr2k8
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
#17
mug51
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


Mug51 has it but you need a scientific calculator which i dont posess at work
#18
probs one online though
#19
I drew it out based on the details & got BC = 7.5m
angle at c = 120, b = 20 & a = 40
probably wrong :whistling:
#20
i get B to be 20.26790106 degrees, so A = 39.73209894

and CB to be 7.380831519
#21
mr.potato_head
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
#22
J9STL;5524436
I drew it out based on the details & got BC = 7.5m
angle at c = 120, b = 20 & a = 40
probably wrong :whistling:

lol look at the answers i got, you pretty much got my answers
#23
mug51
i get B to be 20.26790106 degrees, so A = 39.73209894

and CB to be 7.380831519


Along those lines I get it to be 39.76 degrees and 7.39 m
#24
Thanks for all your help guys, im gonna try and go through all the help in more detail soon :)

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