cos63cos27-sin12sin48 Вычислить
cos63cos27=1/2 (cos(63+27) + cos(63-27))= 1/2 * (cos90 + cos36 ) = 1/2 cos36sin12sin48 = 1/2 (cos(48-12) - cos (48+12)) =1/2 (cos36 - cos60) = 1/2 cos36 - 1/41/2 cos36 - 1/2 cos36 + 1/4 = 1/4
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cos63cos27=1/2 (cos(63+27) + cos(63-27))= 1/2 * (cos90 + cos36 ) = 1/2 cos36
sin12sin48 = 1/2 (cos(48-12) - cos (48+12)) =1/2 (cos36 - cos60) = 1/2 cos36 - 1/4
1/2 cos36 - 1/2 cos36 + 1/4 = 1/4