## RSolve: Recursive function is not a valid variable

RSolve[{ g[n + 1] == g[n] + 10*(g[n]*Cos[-10 Degree] – y[n]*Sin[-10 Degree])/ Sqrt[(g[n]*Cos[-10 Degree] – y[n]*Sin[-10 Degree])^2 + (g[n]*Sin[-10 Degree] + y[n]*Cos[-10 Degree])^2], y[n + 1] == y[n] + 10*(g[n]*Sin[-10 Degree] + y[n]*Cos[-10 Degree])/ Sqrt[(g[n]*Cos[-10 Degree] – y[n]*Sin[-10 Degree])^2 + (g[n]*Sin[-10 Degree] + y[n]*Cos[-10 Degree])^2], g[0] == 100, y[0] == …