- #1
Mdhiggenz
- 327
- 1
Homework Statement
Locate all relative maxima, relative minima ,and saddle points if any.
f(x,y)=ysinx
fx(x,y)=ycosx
fy(x,y)=sinx
ycosx=0 sinx=0
y=0 x=0,∏,2∏... up until infinity
Critical points at (0,0),(∏,0),(2∏,0)...
fxx(x,y)=-ysinx
fyy(x,y)= cosx
fxx*fyy-f(x,y)2→0-0=0 ∴ no relative extrema,
however the book says that fxx*fyy-f(x,y)2=-1 which means saddle point.
I don't understand if y is = to zero.. the function ysinx will always be zero..