In Mathematica 8 the code Limit[ Sin[Sqrt[x^2-1]]-Sin[Sqrt[x^2+1]]]
gives the correct answer 0 but Mathematica 9 and WolframAlpha both give Interval[{-2,2}]
, what is wrong here??
Another problem I encountered is in plotting implicit relation with ContourPlot[ x^(2/3) + y^(2/3) == 4, {x, -7, 7}, {y, -7, 7}]
. It only gives the quarter of the graph!!