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Can someone tell me why my answer is wrong? (Area of triangle) watch

1. So for part (b) I got 36 as the area but the answer is 36 root 3... I've attached my workings out so can someone please tell me where I went wrong?

The answer for part (a) is 48 pi cm^3 btw

Thanks
Attached Images

2. Area of a triangle is 1/2*absin(C). a and b are radii, and C is 2/3 pi
3. (Original post by ℓove)
So for part (b) I got 36 as the area but the answer is 36 root 3... I've attached my workings out so can someone please tell me where I went wrong?

The answer for part (a) is 48 pi cm^3 btw

Thanks
yes

tis no sin 30 but sin 60=

sin 120= sin 180-120= sin 60
4. (Original post by an_atheist)
Area of a triangle is 1/2*absin(C). a and b are radii, and C is 2/3 pi
Oh I used 1/2absin(A) that's why

Thanks
5. (Original post by ℓove)
So for part (b) I got 36 as the area but the answer is 36 root 3... I've attached my workings out so can someone please tell me where I went wrong?

The answer for part (a) is 48 pi cm^3 btw

Thanks
Firstly; you found these red angles by doing cos(A)=... and then proceeded to use the radii sides with an angle that is not between them.

Secondly; you could've just used where a,b are your radii and C is the angle between them (ie the 2/3 pi)

And finally; draw a diagram to prevent mistakes.
6. (Original post by RDKGames)
Firstly; you found these red angles by doing cos(A)=... and then proceeded to use the radii sides with an angle that is not between them.

Secondly; you could've just used where a,b are your radii and C is the angle between them (ie the 2/3 pi)

And finally; draw a diagram to prevent mistakes.
Yeah I realised I could've done it the easier way afterwards.

Nice drawing btw xd
7. (Original post by ℓove)
Yeah I realised I could've done it the easier way afterwards.

Nice drawing btw xd
Thanks. I am a master of drawing on the screen using a mouse as you can see.

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