Подстановка условия
[src](sin(2*l)*l)/cos(l) - sin(l) при l = 1/2
(sin(2*l)*l)/cos(l) - sin(l)
cos(l)lsin(2l)−sin(l) (sin(2*(1/2))*(1/2))/cos((1/2)) - sin((1/2))
cos((1/2))(1/2)sin(2(1/2))−sin((1/2)) (sin(2/2)/2)/cos(1/2) - sin(1/2)
−sin(21)+cos(21)21sin(22) -sin(1/2) + sin(1)/(2*cos(1/2))
−sin(21)+2cos(21)sin(1)