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

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    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
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    Area of a triangle is 1/2*absin(C). a and b are radii, and C is 2/3 pi
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    (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= \dfrac{\sqrt 3}{2}

    \dfrac{\pi}{3} =60 $^{\circ}$

    \dfrac{2 \pi}{3} =120 $^{\circ}$

    sin 120= sin 180-120= sin 60
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    (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
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    (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.
    Name:  Capture.PNG
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Size:  5.7 KB

    Secondly; you could've just used A_{rea}=\frac{1}{2}ab\sin(C) 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.
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    (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.
    Name:  Capture.PNG
Views: 27
Size:  5.7 KB

    Secondly; you could've just used A_{rea}=\frac{1}{2}ab\sin(C) 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
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    (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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