ДОКАЖИТЕ ТОЖДЕСТВО 1)SIN2A-SIN2A*COS2A=SIN4A 2)SINA/1+COSA+CTGA=1/SINA УПРОСТИТЕ...

Question

ДОКАЖИТЕ ТОЖДЕСТВО 1)SIN2A-SIN2A*COS2A=SIN4A

2)SINA/1+COSA+CTGA=1/SINA

УПРОСТИТЕ 1-2SIN2A/2COS2A-1

Answer 1

((sina-cosa)^2-1+sin4a)/(cos2a+cos4a)=(sina^2-2sinacosa+cosa^2-sina^2-cosa^2+sin4a)/(cos2a+cos4a)=(-2sinacosa+sin4a)/ (cos2a+cos4a)=(-sin2a+2sin2a)/(cos2a+2cos2a)=

(sin2a(-1+2))/(cos2a(1+2)= sin2a/3cos2a=tg2a/3