Докажите тождество: tg195 + ctg195 = 4

tg195° + ctg195° =(sin195°/cos195°)+cos195°/sin195°=

= (sin²195°+cos²195°)/(sin195°cos195°)=1/(sin195°cos195°)=

=2/(2sin195°cos195°)=2/sin390°=2/sin(360+30°)=2/sin(30°)=2/(1/2)=4