trolls2 hw10 item6

OR COPY THE FOLLOWING:

mRv@Sub{z}((sin(@DIV{2πv@Sub{z}t;d})-@DIV{2πv@Sub{z}t;d}cos(@DIV{2πv@Sub{z}t;d}))@HAT{i}-(@DIV{2πv@Sub{z}t;d}sin(@DIV{2πv@Sub{z}t;d})+cos(@DIV{2πv@Sub{z}t;d}))@HAT{j}+@DIV{2πR;d}@HAT{k})