✔ 最佳答案
What you have in the diagram is a right triangle, where the fy component intersects the fx component at a 90 deg angle. And that makes F = sqrt(fx^2 + fy^2) the hypotenuse. You best reread about the right triangle and the Pythagorean equation.
So we can employ the trig relationships to find F = fy/sin(theta) = 35/sin(radians(45))) = 4.9497E+01 = 49.5 units. ANS.
But here's where you err. fy, 35cos(45) fx, 35sin(43) are not correct. That 35 is in fact fy = 35 as given. So you really have fy = F sin(theta) to solve for F = fy/sin(theta).