There is an exam on Tuesday.
I have no idea of these problems.
Please help~~ Thank you^^
Compute the directional derivatives of the following functions in the directions indicated.
(a) x²+xy-xz+2y at (2,1,0) in the direction in which the directional derivative is a maximum.
(b) e^xsiny (as a function of two variables) at (0,∏/6) in the direction making a +60˚ angle with the positive x-axis.
(c) x²+2y²-3x+y at (-2,4) in the direction of the tangent (from left to right)of the curve discribed by y=x²
(d) e^xyz+x²+y² at (1,1,1) in the direction of the curve described by x=t, y=2t²-1, z=t³
(e) x²-y²+z² in the direction of the outer normal of ghe surface x²+y²+z=7 at (2,-1,2)