Question

if f(x,y)=cos3xsin4y find df/dx and df/dy at (π/12,π/6)

Answer 1

DF/DX= (6^0.5)/4

Answer 2

fx means that y parts are held constant

fx = -3sin(3x) * sin(4y)


fy means x parts are held constant

fy = cos(3x) * 4cos(4y)


plug in the x and y values the give you to determine the values of fx and fy