Toán Lớp 11: giải phương trình : tan3x = tanx
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Toán Lớp 11: giải phương trình : tan3x = tanx
Comments ( 1 )
tan(3x) – tan(x) = 0
sin(3x)/cos(3x) – sin(x)/cos(x) = 0
sin(3x) – sin(x)cos(3x)/cos(x) = 0 (x với cos(3x))
sin(3x)cos(x) – sin(x)cos(3x) = 0 ( x với cos(3x))
ta có ct
sin(A – B) = sinAcosB – sinBcosA…
sin(3x – x) = 0
sin(2x) = 0
2x = π/2, 3π/2
x = π/4, 3π/4