1. The problem statement, all variables and given/known data A coil with 200 turns of wire is wrapped on an 18.0 cm square frame. Each turn has the same area, equal to that of the frame, and the total resistance of the coil is 2.0Ω . A uniform magnetic field is applied perpendicularly to the plane of the coil. If the field changes uniformly from 0 to 0.500 T in 0.80 s, find the magnitude of the induced emf in the coil while the field has changed 2. Relevant equations emf =N* (Δ(BAcosθ) / Δt) 3. The attempt at a solution I'm having trouble understanding the answer to the problem. In a solution to this question I seen, the answer is gotten from doing this calculation: emf = [(200)*(0.500-0)*(0.18*0.18)*cos 90] / 0.80 and the answer equals to 4.10 V. What I don't understand is why do you multiply by the cos 90? cos 90 in degrees is 0 and in radians it is -0.4480736.... Doing the calculation without the cos 90 will get that answer, so why is it in the equation?