In △ ABC, if 3a2 + 3b2-3c2 + 2Ab = 0, then Tanc=______ ．

∵ in △ ABC, 3a2 + 3b2-3c2 + 2Ab = 0, i.e. A2 + b2-c2 = - 23ab, ∵ according to cosine theorem, COSC = A2 + B2 − c22ab = - 23ab2ab = - 13 < 0, i.e. C is obtuse angle, ∵ sinc = 1 − cos2c = 223, then Tanc = sinccosc = - 22

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