theorem
  integral(r(#)cos,A) = r*sin.(upper_bound A) - r*sin.(lower_bound A)
proof
A1: [#]REAL is open Subset of REAL;
  cos is_integrable_on A & cos|A is bounded by Lm11;
  hence thesis by A1,Th27,Th68,SIN_COS:68;
end;
