See Ting Xuan's answer to Jason Lim's Secondary 3 A Maths Singapore question

Ting Xuan's answer to Jason Lim's Secondary 3 A Maths Singapore question.

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Date Posted: 3 years ago

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Eric Nicholas K

3 years ago

No; you missed out the rejection of the negative solution, since angle A being obtuse implies angle A/2 being acute, meaning to say that sin (A/2) must have a positive value.