sin 390 cos 420 tg 780 ctg 405

sin 390 cos 420 tg 780 ctg 405=?

sin390=sin (360+30) = sin30=1/2

cos420=cos (360+60) = cos60=1/2

tg780=tg (360*2+60) = tg60=sqrt{3}

ctg405=ctg (360+45) = ctg45=1

sin 390 cos 420 tg 780 ctg 405=1/2 * 1/2 * sqrt{3} * 1=sqrt{3}/4