Possible Duplicate:
Derivative of Determinant Map
consider $v=(v_1,v_2)\in \mathbb{R}^2$ ,$w=(w_1,w_2)\in\mathbb{R}^2$ consider the determinant map det:$\mathbb{R}^2\times \mathbb{R}^2$ define by $\det(v,w)=v_1w_2-w_1v_2$. The derivative of the determinant map at $(v,w)\in\mathbb{R}^2\times \mathbb{R}^2$ evaluated on $(H,K)\in \mathbb{R}^2\times \mathbb{R}^2$ is
$1$. $\det(H,W) +\det(V,K)$
$2$. $\det(H,K)$
$3$. $\det(H,V)+\det(W,K)$
$4$. $\det(V,W) + \det(K,W)$.
Well, I have no idea how to solve this one.