0已知函数f(x，y)-x2+y2-xytan(x/y)，求f(tx，ty)．

0已知函数f(x，y)-x²+y²-xytan(x/y)，求f(tx，ty)．
【正确答案】：f(tx，ty)=(tx)²+(ty)²-(tx)•(ty)tan(tx/ty) =t²x²+t²y²-t²xytan(x/y) =t²(x²+y²-xytanx/y) =t²f(x，y)．