Roman C. answered 10/16/15
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Masters of Education Graduate with Mathematics Expertise
ex cos x = 1 + sin xy
ex cos x + ex (-sin x) = cos xy · d/dx (xy)
ex (cos x - sin x) = (y + x · dy/dx) cos xy
y + x · dy/dx = ex (cos x - sin x) / cos xy
dy/dx = ex (cos x - sin x) / (x cos xy) - y/x