tan(a+π/4)=1/2求sin2a-cosa的平方/1+cos2a

tan(a+π/4)=1/2求sin2a-cosa的平方/1+cos2a
tan(a+π/4)=1/2求sin2a-cosa的平方/1+cos2a

tan(a+π/4)=1/2求sin2a-cosa的平方/1+cos2a
tan(a+π/4)=(tana+1)/(1-tana)=1/2 tana=-1/3
sin2a-cosa的平方/1+cos2a=(2sinacosa-(cosa)^2)/2(cosa)^2=(2sina-cosa)/2cosa=(2tana-1)/2=-5/6