Final answer:
To find the electric field at the given points, we can use the formula E = Q/A, where E is the electric field, Q is the charge, and A is the area.
Step-by-step explanation:
To find the electric field at the given points, we can use the formula E = Q/A, where E is the electric field, Q is the charge, and A is the area. Since the electric field density for the sheet is given as 58 nC/m² and the sheet is a square with sides of 5m, the total charge Q would be Q = 58 nC/m² * 5m² = 290 nC.
Now, to find the electric field at the points (5,8,20), we need to consider the distance from the point to the sheet. The distance from the point to the sheet is calculated as the difference in the x and y coordinates. In this case, the distance is d = |5-5| + |8-5| = 8.
Using the equation E = Q/A and plugging in the values, we get E = 290 nC / 8 = 36.25 nC/m².