Let f: r> r be defined by ay)-(1). y0 0, y = 0 if the directional derivative of f at (0,0) exists along the direction cosa î + sina j, where sin a# 0, then the

Let f: R> R be defined by ay)-(1). y0 0, y = 0 If the directional derivative of f at (0,0) exists along the direction cosa î + sina j, where sin a# 0, then the value of cota is