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Tasneem Raslan: There's a question that I'm confused about, and I'd really appreciate some help. There's a circle, and two radii that extend to form a chord AB. The minor angle is given as 2O rads, and the question is to find the an expression for the chord in terms of r (radius) and O. I need to find the chord using the sine rule, but no matter what I do, my answer doesn't match the mark scheme. If you ask, I did sin2O/(AB) = sin((π-2O)/2)/r. The mark scheme says the answer is 2rsinO, but my answer includes π. Thanks in advance.
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  • October 23, 2016 at 4:15pm
  • Shu Yun:You are on the right track, but just half way there. From your working, you have to apply addition formula to sin(π-2O), which is sin(α + β) = sinα cos β + cos α sin β. Besides, you also have to apply double angle formula to sin2O, which is sin2α=2sinα cos α. Evaluate the expression and you'll get the answer.
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    • October 25, 2016 at 4:53am
  • Shu Yun:Pardon my mistakes, it's *sin(α - β) = sinα cos β - cos α sin β
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    • October 25, 2016 at 4:54am
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