kill(all)$

Van = facebook.com/LearningCalculus$

    Is this letter 'o', or zero '0', or degrees (°)?
     Case 1: x^o

f(x):=sec(x^o)*tan(x^o)$

declare(o,integer)$

'integrate(f(x),x);

changevar(%,u-x^o, u,x);

    Case 2: x^0;

f(x):=sec(x^0)*tan(x^0)$

integrate(f(x),x)+C;

    Case 3: x is in units of degrees (°) 

deg2Rad(u):=u*%pi/180$
rad2Deg(u):=u*180/%pi$

f(x):=sec(deg2Rad(x))*tan(deg2Rad(x))$ f(x)$

integrate(f(x),x)+C$

F(x):= C + rad2Deg(sec(rad2Deg(x)))$ F(x);