Question

if A = cos(xy)i + ( 3xy + 2x ^2 )j - (3x + 2y )k find d^2A/dy^2 and d^2A/dxdy

Answer 1

$\frac{dA}{dy}=-xsin(xy)i+3xj-2k$

$\frac{d^2A}{dy^2}=-x^2cos(xy)i$

$\frac{d^2A}{dxdy}=(-sin(xy)-xycos(xy))i+3j$