Докажите тождество cos^2 a - cos^4 a + sin^4 a = sin^2 a

Question

Алгебра: Докажите тождество cos^2 a - cos^4 a + sin^4 a = sin^2 a

hs2 · Answer

cos^2 a - cos^4 a + sin^4 a = cos^2 a  + sin^4 a - cos^4 a =  cos^2 a + (sin^2 a -  cos^2 a)(sin^2 a +  cos^2 a) = cos^2 a + (sin^2 a -  cos^2 a)*1 = cos^2 a + sin^2 a -  cos^2 a = sin^2 a...

Докажите тождество cos^2 a - cos^4 a + sin^4 a = sin^2 a

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