remove oftype from derivative definitions

Author: mlubin

src/differentiate.jl

@@ -160,8 +160,8 @@ symbolic_derivative_1arg_list = [
     ( :asech,       :( -1 / x / sqrt(1 - x^2)                   ))
     ( :acsch,       :( -1 / abs(x) / sqrt(1 + x^2)              ))
     ( :acoth,       :(  1 / (1 - x^2)                           ))
-    ( :deg2rad,     :(  oftype(x, pi) / 180                     ))
-    ( :rad2deg,     :(  180 / oftype(x, pi)                     ))
+    ( :deg2rad,     :(  pi / 180                                ))
+    ( :rad2deg,     :(  180 / pi                                ))
     ( :erf,         :(  2 * exp(-x*x) / sqrt(pi)                ))
     ( :erfinv,      :(  0.5 * sqrt(pi) * exp(erfinv(x) * erfinv(x))  ))
     ( :erfc,        :( -2 * exp(-x*x) / sqrt(pi)                ))