Hi

I need help with the followoing question:

Find the slopes of the curves of intersection of the surface z= f(x,y) with the planes perpendicular to the x axis and y axis respectively at a given point.

z= sin (4x+y) at (0, pi/2)

I did fx(x,y)= 4 cos(4x+y) and at this point i get 0

To find the perpendicular planes i think you do -1/0 but that is not defined.

is this the correct method?

kind regards