Докажите торжества 1.sin^4a+2sinacosa-cos ^4a =cos(3п - вопрос №785572114243 от saskey 20.03.2023 19:23

Question

Алгебра: Докажите торжества 1.sin^4a+2sinacosa-cos ^4a =cos(3п решите, нужно

saskey · Answer

[(sin²a-cos²a)(sin²a+cos²a)+sin2a]:(sina2/cos2a -1) - cos2a=
=(-cos2a+sin2a):(sin2a-cos2a)/cos2a -cos2a=
=(-cos2a+sin2a) *cos2a/(sin2a-cos2a) - cos2a=cos2a-cos2a=0

(2sin3acos2a+sin3a)/(2cos3acos2a+cos3a)=
=sin3a(2cos2a+1)/cos3a(2cos2a+1)=sin3a/cos3a=tg3a