Доказать тождество: (1+sin2α+cos2α)/(1+sin2α-cos2α)=ctg α

(1+sin2a+cos2a)/(1+sin2a-cos2a)=(1+2sina*cosa+cos^2 a-sin^2a)/(1+2sina*cosa-cos^2 a+sin^2 a)=(2sina*cosa+2cos^2a)/(2sina*cosa+2sin^2a)=2cosa(sina+cosa)/2sina(sina+cosa)