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Arata-ti ca: 4sinpi/12cospi/12=1

Răspuns :

cos^2(x)=(1+cos2x)/2

cos^2(x)=(1+cos2x)/2

sin(pi/12)^2 * cos(pi/12)^2 = ((1-cos(pi/6))/2)*((1+cos(pi/6))/2) 


(1-cos^2(pi/6))/4=(1-3/4)/4=1/16