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1. c2 help
Could some one please tell me where I am going wrong in answering this question

basically you have to find the angle

so i use the cosine formula

cosA= c^2 + b^2 - a^2/ 2bc

a=18.4
b=20
c=10

so cosa= 100+400 - 338.56/ 400=

cosA= 0.4036

however in the mark scheme it says

cos A= 0.3998

could some one please tell me why my answer is different to the one in the mark scheme
2. Re: c2 help
Because you rounded off the 18.4.............
3. Re: c2 help
(Original post by unknown123)
Could some one please tell me where I am going wrong in answering this question

basically you have to find the angle

so i use the cosine formula

cosA= c^2 + b^2 - a^2/ 2bc

a=18.4
b=20
c=10

so cosa= 100+400 - 338.56/ 400=

cosA= 0.4036

however in the mark scheme it says

cos A= 0.3998

could some one please tell me why my answer is different to the one in the mark scheme
You have rounded TOO SOON, your 338.56 is wrong It should be 340.07

I think you squared 18.4 instead of 18.441 ALWAYS use the best figure available.
4. Re: c2 help
wait, which question are you talking about?
5. Re: c2 help
question 4)ii

I now know why it was wrong.

thanks guys
6. Re: c2 help
merked the last question