Question

найти знач. выражения -4*корень3 cos(-930градусов)

Answer 1

$-4 sqrt{3}* cos(-930^o)=-4 sqrt{3}* cos930^o=-4 sqrt{3}* cos(1080^o-150^o)=\ = -4 sqrt{3}* cos(-150^o)=-4 sqrt{3}* cos150^o=-4 sqrt{3}* cos(90^o+60^o)=\ = -4 sqrt{3}* (-sin60^o)=-4 sqrt{3}* (- frac{ sqrt{3} }{2} )=6$

Answer 2

$-4* sqrt{3} *cos(-930)= \ =-4 sqrt{3} cos930= \ =-4 sqrt{3} cos(1080-150)= \ =-4 sqrt{3} cos150= \ =-4 sqrt{3} cos(180-30)= \ =-4 sqrt{3} cos30=4 sqrt{3} * frac{ sqrt{3} }{2} = \ = frac{x4 sqrt{3} * sqrt{3} }{2} = frac{4*3}{2} =2*3=6$