Rappel
🔸cos2x+sin2x=1
🔸tanx=cosxsinx
1
1+tan2x =1+(cosxsinx)2 =1+cos2xsin2x =cos2xcos2x+cos2xsin2x =cos2xcos2x+sin2x=cos2x1 =sin2xsin2x+cos2x
2
1+tan2x1 =1+cos2xsin2x1 =1+sin2xcos2x =sin2xsin2x+sin2xcos2x =sin2xsin2x+cos2x =sin2x1
3
cos2x−sin2x =(1−sin2x)−sin2x =1−2sin2x
4
(cosx+sinx)2 =1cos2x+sin2x+2cosxsinx =1+2cosxsinx
5
(cosx−sinx)2 =1cos2x+sin2x−2cosxsinx =1−2cosxsinx