Ответ №1
[cos(2π-π/12)]^4 - [sin(π+π/12)]^4 = (cosπ/12)^4 -(-sinπ/12)^4 =
= (√(1+cosπ/6)/2)^4 - (√(1-cosπ/6)^4 = (1+√3/2)²/16 - (1-√3/2)²/16=
= 1/16 ·(1+√3/2+1-√3/2)(1+√3/2-1+√3/2) =
=1/16· 2·√3 = √3/8
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