1. The problem statement, all variables and given/known data We have a coil with cross-sectional area of 2.4m^2. Magnetic flux density is of 0.29T Number of turns are 1. Initially the coil is parallel to magnetic field lines. (Coil's normal vector is perpendicular to field vector) Calculate the change in magnetic flux when coil is moved through an angle of 1 degrees 2. Relevant equations ΔΦ = ΔBAcosθ 3. The attempt at a solution My attempt ΔΦ = ΔBAcosθ ΔΦ = BA Δcosθ ΔΦ = BA (cos 89 - cos 90) Which leads to a correct answer Examiner attempt ΔΦ = ΔBAcosθ ΔΦ = BA Δcosθ ΔΦ = BA cos (90-1) How do they do this? Which leads to a correct answer Another question inquired me to calculate the change of flux when the change in θ is from 0 to 90. I used the normal way of multiplying BA by (cos 90 - cos 0). However, the examiner stated that this is simplified treatment, a rigorous method would involve averaging of cos θ leading to a factor of 1/sqrt2. How is this factor achieved? I tried to calculate the mean value of cos θ using integration but the answer was different.