双扭线r(来学网)=2acos2θ所围成图形的面积是:
  • A.
    2a(来学网)cos2θdθ
  • B.
    4a(来学网)cos2θdθ
  • C.
    4a(来学网)cos2θdθ
  • D.
    (来学网)