А) cos(180°+a)cos(-a) / sin(-a)sin(90°+a) = -cos a × cos a / -sin a × cos a =
cos a / sin a = ctg a
б) sin(π-t)cos(2π-t) / tg(π-t)cos(π-t) = sin t ×cos t / -tg t × (-cos t) =
sin t × cos t / tg t × cos t = sin t / tg t = sin t / (sin t / cos t) = cos t
в)sin(-a)ctg(-a) / cos(360°-a)tg(180°+a) = -sin a × (-ctg a) / cos a × tg a =
(sin a × cos a / sin a) / (cos a × sin a / cos a) = cos a / sin a = ctg a
г) sin(π+t)sin(2π+t) / tg(π+t)cos(3π/2 +t) = - sin t × sin t / tg t × sin t =
- sin t / tg t = - sin t / (sin t / cos t) = - cos t