упрастите выражение
Cos (п\4 +a) cos(п/4-a)+1\2sin в квадрате a
cos 2a- cos a * cos 3a
1) (cos 2a+cos(п/2))/2 + (sin^2 a)/2 = (1/2)*cos(a).
2) cos 2a- (1/2)*(cos 2a+cos 4a) = (1/2)*(cos 2a-cos 4a) = sin 3a*sin a.
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Answers & Comments
1) (cos 2a+cos(п/2))/2 + (sin^2 a)/2 = (1/2)*cos(a).
2) cos 2a- (1/2)*(cos 2a+cos 4a) = (1/2)*(cos 2a-cos 4a) = sin 3a*sin a.