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Help with maths question

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Original post by Incarcarus
1/2 a b sin (c) = area

c = sin-1 (10.5 / 1/2*4*7)
c = 48

Using a^2=b^2+c^2-2bc cos(A)
the final side length turns out to be 5.2 which cannot be correct

This is 100% the same as the one in the exam question https://imgur.com/a/Tv4I3Mt so should be correct.
Original post by Incarcarus
1/2 a b sin (c) = area

c = sin-1 (10.5 / 1/2*4*7)
c = 48

Using a^2=b^2+c^2-2bc cos(A)
the final side length turns out to be 5.2 which cannot be correct

This is not correct because we know that the angle x is the largest. Therefore, you can do 180-48.59 = 131.41. Using this to find the opposite side will give you 10.1cm, which makes more sense as it is the longest side.
Therefore, tan(x) = -1.13
Original post by meggie16
This is not correct because we know that the angle x is the largest. Therefore, you can do 180-48.59 = 131.41. Using this to find the opposite side will give you 10.1cm, which makes more sense as it is the longest side.
Therefore, tan(x) = -1.13

Yes, thank you, I was incorrect :smile:
1/2(7)(4)sinx=10.5
1/2(28)sinx=10.5
sinx=10.5/14
x=sin^-1(3/4)
x=48.59 degrees

therefore tan(48.59)=1.13 or 1.1 what you got.
Original post by meggie16
This is not correct because we know that the angle x is the largest. Therefore, you can do 180-48.59 = 131.41. Using this to find the opposite side will give you 10.1cm, which makes more sense as it is the longest side.
Therefore, tan(x) = -1.13

Thank you!

I actually got it correct! It just doesn't seem like it would be the correct answer.
Original post by Goldfish4343
Thank you!

I actually got it correct! It just doesn't seem like it would be the correct answer.

Np :smile: mark schemes tend to be wrong a lot haha

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