Toán Lớp 11: giải pt :
a,sin ²x+cosx .cos3x+sin2x.cos2x=0
b,
(cosx-1)(2cosx-1)/sinx =1-sin2x+2cosx^2
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Toán Lớp 11: giải pt :
a,sin ²x+cosx .cos3x+sin2x.cos2x=0
b,
(cosx-1)(2cosx-1)/sinx =1-sin2x+2cosx^2
Comments ( 2 )
a)
sin²x + 1/2(cos2x + cos4x) + 1/2sin4x = 0
1-cos2x/2 + 1/2cos2x = -( 1/2sin4x + 1/2cos4x)
-sin(4x + π/6)= 1/2
sin(4x + π/6) = -1/2
4x+π/6 = -π/6 +k2π x = -π/3 + kπ/2
4x+π/6 = 7π/6 + k2π x = π + kπ/2