Ответы на вопрос:
1) cos(285*)*cos(165*) = (1/2)*( cos(285*+165*) + cos(285*-165*) ) == (1/2)*( cos(450*) + cos(120*) ) = (1/2)*( cos(360*+90*) + cos(180*-60*) ) = (1/2)*(cos(90*) - cos(60*) ) = (1/2)*( 0 - (1/2)) = -1/4 = -0,25 2)sin75+sin 15 = 2sin (75+15)/2 * cos (75-15)/2 = 2sin 45*cos30
(7x+5)(12x-2) = (14x+1)(6x-4)
84x²+46x-10 = 84x²-50x-4
84x²+46x-10-84x²+50x+4 = 0
96x-6 = 0
96x = 6
x = 6/96
x = 1/16.
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