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Question Number 21430 by Tinkutara last updated on 23/Sep/17

$$\mathrm{In}\mathrm{any}\mathrm{\Delta }ABC,\mathrm{the}\mathrm{value}\mathrm{of}$$$$2ac\sin \left(\frac{A-B+C}{2}\right)\mathrm{is}$$

Answered by $@ty@m last updated on 23/Sep/17

$$=2ac\sin \left(\frac{\pi -2B}{2}\right)$$$$=2ac\cos B$$$$=c^2+a^2-b^2$$

Commented by Tinkutara last updated on 23/Sep/17

$$\mathrm{But}\mathrm{book}\mathrm{says}{b}^2-a^2-c^2.\mathrm{I}\mathrm{also}\mathrm{think}$$$$\mathrm{your}\mathrm{answer}\mathrm{true}\mathrm{because}\mathrm{I}\mathrm{also}\mathrm{got}\mathrm{the}$$$$\mathrm{same}\mathrm{answer}.$$

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