kill(all)$

van=facebook.com/LearningCalculus;

pi:%pi;

n:2*(sin(17*pi/9)*cos(10*pi/9)-sin(10*pi/9)*cos(17*pi/9))*sin(13*pi/9)*cos(25*pi/18)$
d:-sin(23*pi/18)+2*sin(10*pi/9)*sin(13*pi/9)*sin(17*pi/9)*cos(25*pi/18)+2*sin(13*pi/9)*cos(10*pi/9)*cos(25*pi/18)*cos(17*pi/9)$

%alpha:atan(n/d);

bfloat(%);

float(%*180/pi);