Sec(x)=-41/9
cos(x)=-9/41
sin(x)=-корень(41^2-9^2)/41=-40/41
tg(x)=-40/41 : -9/41 = 40/9
ctg(x) = 1 : 40/9 = 9/40
sin(x)/(sin^2(x) - cos^2(x)) + cos(x)/(cos^2(x) - sin^2(x)) =
= sin(x) - cos(x) /(sin^2(x) - cos^2(x)) =
= 1 /(sin(x) + cos(x))
ОДЗ: x не равно pi/4 + pi*k/2
sin(pi/15)*cos(3*pi/5)+cos(pi/15)*sin(3*pi/5) =
= sin(pi/15+3*pi/5) = sin(pi/15+9*pi/15) = sin(10*pi/15) =
= sin(2*pi/3) =КОРЕНЬ(3)/2