C4 angles question aqa

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    Hey I came across this question 2aii in Jan 2012 C4 and the mark scheme wants me to use pythagoras but how do I do that if the angle is obtuse by pythagoras I could calculate the actute angle which would be (1/sqrt(3)) but then hwo would I find the obtuse one from that which is -1/sqrt(3). I just did sin inverse 0.5 then found the obtuse angle 180-30 and then 'tan'ed that. But the mark scheme wangs use of pythagoras... My working and the mark scheme and the question have been attached. Thanks. Btw I got this exam tomorrow AQA . The question is 2a ii btw
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    It tells you in the question that angle B is obtuse, tan of an obtuse angle is negative which is why the answer is negative ie -1/sqrt(3)
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Updated: June 13, 2012
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