1. The problem statement, all variables and given/known data I am working through Boas' Mathematical Methods in the physical sciences book and I don't understand the triple scalar product and torque example. k [dot] (r X F) = 0 0 1 = xF_y - yF_x x y z F_x F_y F_z k is on the z axis and points in the positive direction. r points in the positive x y and z direction. F points downward in the z direction and it is positive in the x and y direction. She says "the x and y components of the force can be seen better if we draw them in the (x,y) plane. The torque about the z-axis produced by F_x and F_y is xF_y - yF_x by the elementary definition of torque." 2. Relevant equations 3. The attempt at a solution I understand that torque is rFsin theta but I don't understand why it isn't xF_x and yF_y I don't understand why she is subtracting yF_x from xF_y. They are not negative.