Question

若cos(π+α)=-1/2,3π/2

Answer 1

cos(π+α)= sin(-π/2 -α)= -sin(π/2 +α)= -cos(-α)= -cosα= -1/2

则cosα＝1/2,

sin(2π-α)＝sin(-α)= -sinα

3π/2