Question

sin(-420гр) * ctg675гр.

Answer 1

sin(-420)=-sin420=-sin(360+60)=-sin60=-sqrt3/2

ctg675=ctg(3*180+135)=ctg135=ctg(180-45)=-ctg45=-1

-sqrt3/2*(-1)=sqrt3/2

Answer 2

sin(-420°)·ctg675° = 

 = sin(-360°- 60°)·ctg(2·360°- 45°) =

=  sin(- 60°)·ctg(- 45°) =

=  -sin60°·(-ctg 45°) =

= - 0,5√3 ·(-1) =

= 0,5√3