Tan^-1(x^2-y^2/x^2 y^2)=a 223599-X^(2)y^(2)-tan^(-1)sqrt(x^(2)+y^(2))=cot^(-1)sqrt(x^(2)+y^(2))

The equation of the tangent line is then y1=4(x2) We have plotted a graph of the equation and the tangent line in Figure 240 using the implicit plot mode of our computer algebra system Our