Simplifying sin ^ 2 A + cos a * cos (60 + a) - Sin ^ (30-a)=
Sin ^ 2A + cos a * cos (60 + a) - Sin ^ 2 (30-a) = sin ^ 2A + cosa (COSA * cos60 Sina * sin60) - (sin30 * cosa Sina * cos30) ^ 2 = sin ^ 2A + 1 / 2cos ^ 2A - Factory 3 / 2sina * cosa-1 / 4cos ^ 2A + factory 3 / 2sina * cosa-3 / 4sin ^ 2A = 1 / 4sin ^ 2A + 1 / 4cos ^ 2A = 1 / 4
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