Докажите тождество sin(a+π)/sin(a+3π/2) + cos(3π-a)/(cos(π/2+a)-1) = 1/cosa
100
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Ответы на вопрос:
Sin(a + π) = -sinasin(a + 3π/2) = sin(a + π + π/2) = -sin(a + π/2) = -cosacos(3π - a) = cos(2π + π - a) = cos(π - a) = -cosa cos( π/2 + a) = -sina-sina/(-cosa) - cosa/(-sina - 1) = sina/cosa + cosa/(sina + 1) == [sina(sina + 1) + cos²a)]/(sinacosa + cosa) = (sin²a + cos²a + sina)/(sinacosa + cosa) = (1 + sina)/cos(1 + sina) = = 1/cosa, чтд
0,7^12·0.7^(-15): 0.7^(-2) =
= 0,7^12·0.7^(-15)·0.7^2 =
= 0.7^(12-15+2) = 0.7^(-1) = 10/7
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