Решите пожалуйста,и если можно объясните )

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Andryuhatab

14 апр. 2013 г., 22:08:57 (11 лет назад)

π=180
315= 360-45 = 2π - π/4
7π/4= 8π/4 - π/4 = 2π - π/4
-5π/3=π/3 - 6π/3 = π/3 -2π
tg x = sin x / cos x
sin 2x = 2 sin x · cos x
sin π/3 = (√3)/2
cos π/3 = 1/2  
sin π/2 = 1
sin(2π - π/4) =sin (-π/4) = - sin π/4
cos (2π- π/4) = cos(-π/4) = cos π/4
sin 315 · cos 7π/4 - 2 tg (-5π/3) = -sin π/4 · cos π/4 - 2 (sin π/3) / (cos π/3) =
= -1/2 sin 2π/4 - 2 (√3 /2)/(1/2) = -1/2 sin π/2 - 2 √3=-1/2 ·1 -2√3=-1/2-2√3