求sin40°+cos²40°

求sin40°+cos²40°
求sin40°+cos²40°

求sin40°+cos²40°
应该是sin²40°+cos²40°吧,如果是,
则sin²40°+cos²40°＝1

用到积化和差公式和倍角公式 sinαsinβ=-[cos(α+β)-cos(α-β)]/2 cos^2 α=1/2(1+cos2α) sin^2 40°+cos^2 10°-sin40°