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o, I've come across a sine rule question that looks like the diagram in the following link, with angle ACB=120, b=6cm and sine angle CDB= 1/root12.

Using the sine rule, I work out AB=18cm. But when I divide triangle ABC into two separate right-angled triangles ACD and BCD and use Pythagoras Theorem to work out AB, I got root 11 + root 35. What went wrong? (since sine CDB = 1/root 12, x=1 and a=root12, then DB =root 11 then I do the same for triangle ACD)

[1]: https://mathspace.co/images/gen/?params=ColoredRegion(img_path='/media/upload/images/10-furthertrig/11621-2.png',theme='dark')&src=/media/upload/images/10-furthertrig/11621-2.png&signature=f000ed2fa74fc13aa0de740f04f949e1d197db35&invert_color=1 [1]: https://mathspace.co/images/gen/?params=ColoredRegion(img_path='/media/upload/images/10-furthertrig/11621-2.png',theme='dark')&src=/media/upload/images/10-furthertrig/11621-2.png&signature=f000ed2fa74fc13aa0de740f04f949e1d197db35&invert_color=1

Posted in Trigonometry, asked by Tom, 2 years ago. 864 hits.
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