Problem 4. consider the case of a flat vortex sheet of strength (s) at an angle of attack in a uniform freestream of velocity v[infinity]. (a) show that the pressure difference across the sheet is equal to ∆p = rhov[infinity]γcosα (tip: find the normal and tangential velocity components on each side of the sheet and then apply bernoulli’s equation.) (b) show that the lift per unit span developed by the sheet is l 0 = rhov[infinity]γ for small angle of attack. (tip: use the result for from part (a))