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Trig addition rule question

Sin((pi/3)-y)=cos(y+(5pi/6))

I expand this as normal but then I get to a point where I have tan(y)=0/0 which is obviously indeterminate and whichever way I go, I always end up with this? Where have I gone wrong? Will attach full working
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ElCorleone
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Original post by ElDonCorleone
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Your working should lead to tan⁡y=−30\tan y=-\dfrac{\sqrt 3}{0}.

So tan⁡y\tan y is undefined.

tan⁡y\tan y is undefined when cos⁡y=0\cos y=0 since tan⁡y=sin⁡ycos⁡y\tan y = \dfrac{\sin y}{\cos y}. So tan⁡y\tan y is undefined at π2+nπ.\dfrac{\pi}{2} + n \pi.
(edited 6 years ago)

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