kill(all)$

van=facebook.com/LearningCalculus$

y:factor(((cos((α*2))*x*(-1))+((cos((α*2)))^((-1))*x)));

x/y;

substitute(t,α,%);

substitute(x,t,%);

solve(r*cos(theta)/r*sin(theta),r);

X/Y=-cos(2*t)/((cos(2*t)-1)*(cos(2*t)+1));

solve(%,Y);