Answer:
The angle between the electric field and sheet's normal vector is 80.96 degrees.
Step-by-step explanation:
Given that,
Area of the flat sheet,

Electric field, E = 10 N/C
Electric flux of the sheet,

The electric flux is through the sheet is given by the dot product of electric field and the area vector. It is given by :

or

is the angle between electric field and sheet's normal vector
So,




So, the angle between the electric field and sheet's normal vector is 80.96 degrees. Hence, this is the required solution.