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maths cosine rule help

Attachment not found

I can't get the right answer
Original post by Sammyboy1234
Attachment not found

I can't get the right answer


So then post your working out and we'll see where you're going wrong.

EDIT: The angle between the two is not 55. It's 90+35
(edited 6 years ago)
all I have done is used the cosine rule and gotten 281 for the distance
Attachment not found x.x
Original post by Sammyboy1234
all I have done is used the cosine rule and gotten 281 for the distance


Yes this is clear, but what numbers did you use for the cosine rule.

Also, the attachment is gone.
35 squared +270 squared - 2 ×35×270×cos105
then squared root 79016....
gives you 281
Screenshot_20180228-221454-compressed.png.jpeg
Original post by Sammyboy1234
...


Firstly, when using a2+b2−2abcos⁡θa^2+b^2-2ab \cos \theta, note that a,ba,b are actually the lengths of the lines. Right now you have these lengths labelled as their bearings for some reason. Secondly, θ\theta is the angle between the two arrows - it is not 105.

Lastly, we are interested in the distance between the two objects AFTER 2 hours. So when it comes to a,ba,b values, they need to represent distances of both ships from the Port after 2 hours.
image-6a9bf1bb-10b6-4a99-91ba-cf5edb63acbc1741172346-compressed.jpg.jpeg
would I need to use the speed distance over time formula
Original post by Sammyboy1234
would I need to use the speed distance over time formula


To work out how far away each ship is from the Port, yes.

speed×time=distance\text{speed} \times \text{time} = \text{distance}

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