You will find attached your question which I edited. I reversed the image to be more on the positive side of the axes.
Taking the quiz in "Deferred feedback" mode greatly simplifies the work. Note that students must enter something, anything, in each of the answer boxes. I added a message and blocked the navigation buttons if an answer box is empty. This is important
because otherwise their score will be zero.
The question uses random data. It works for any values of the forces A, B and C as long as they act in the quadrant shown in the figure. I also indicated, in the Variables field, a data set which gives only positive values of theta, which would be easier
for the students. Note in passing the convention I used for the values of theta.
One of the difficulties is that the calculated values can be positive or negative and therefore the interval of validity of say plus or minus 1% is different in the two cases.
The other difficulty is to properly adjust the grading criteria so as not to penalize students more than once for the same error. The question works as explained below.
If the sum Ax + Bx + Cx is correct, the student gets a point even if the values of Ax, Bx or Cx are incorrect, and similarly for Ay + By + Cy.
If the calculation for R is correct, the student gets a point even if the values of Rx and Ry are incorrect. Note that the student does not get a point for a negative value of R.
If the calculation of theta is correct based on values of Rx and Ry which are either 1) correct, 2) calculated correctly from incorrect values of Ax, Bx, ... or 3) simply incorrect, the student gets a point.
The question might still need some debugging.