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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 reall… Read More

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

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

Options

## All Comments

(24) Jump to unreadPost a commentthougth that only applied to a right angled triangle.

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

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

the angle BCA = 120 degs?

a2 = 16 b2 = 100 c2 = 116

sooo length CB must be = 10.770329614269007 ???

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

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

so BCA must be 60

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

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

angle at c = 120, b = 20 & a = 40

probably wrong :whistling:

and CB to be 7.380831519

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

angle at c = 120, b = 20 & a = 40

probably wrong :whistling:

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

and CB to be 7.380831519

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