sin 390 cos 420 tg 780 ctg 405

Question

sin 390 cos 420 tg 780 ctg 405

Answer 1

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