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cos^3 x + 1/(cosec^3 x) = 0
cos^3 x + sin^3 x = 0
sin^3 x = - cos^3 x
(sin^3 x)/(cos^3 x) = (- cos^3 x)/(cos^3 x)
tan^3 x = -1
tan x = -1
tan x = Tan 135° = Tan 315°
1) x = 135°
Sin 2x = 2 sin x cos x = 2 sin 135° cos 135° = 2 . 1/2 √2 . -1/2 √2 = -1
2) x = 315°
Sin 2x = 2 sin x cos x = 2 sin 315° cos 315° = 2 . -1/2 √2 . 1/2 √2 = -1

cos^3 x + 1/(csc^3 x) = 0
cos^3 x + sin^3 x = 0
cos^3 x = -sin^3
(cos^3x / -cos^3) = (-sin^3x)/(-cos^3)
-1 = tan^3x
tan x = -1 ( A )