R 1=sin(sym(0.3)) is the result of sym symbolic operation, sym(0.3)=3/ 10, and then sin(3/ 10) becomes symbolic operation.

R2=sym(sin(0.3)) means to do sin(0.3)=0.2955 first. . . . Then the result of sym(0.29) becomes a fraction. Although the last two answers are sym, the results are different.

Just compare vpa(r 1) and vpa(r2). Theoretically, the accuracy of r 1 is infinite, while the accuracy of r2 is limited.