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Cos a b. Cos2b. Cos a/2+b/2 cos a/2-b/2. 2cos a+b/2 cos a-b/2. Докажите тождество cos(2a+2b)=cos2(a+b).
Cos2b. Cos a/2+b/2 cos a/2-b/2. 2cos a+b/2 cos a-b/2. Докажите тождество cos(2a+2b)=cos2(a+b).

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