sin 2 ⁡ 120 ∘ 等于( )

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-sin2-cos2 -sin2+cos2 sin2+cos2 sin2-cos2

1/3*sin(1/2)*sin(1/2) sin(0.5)*sin(0.5)/3 pow(sin(0.5),2)/3 1/3.0*pow(sin(1.0.2),2)

2sin α cos β= sin( α+β) +sin( α-β) 2sin α cos β= cos( α+β) +sin( α-β) . 2sin α cos β= sin( α+β) -sin( α-β) 2sin α cos β= cos( α+β) -sin( α-β)

sin 1sin 2sin 3sin3

sin 2α= 2sin α cos α sin 2α= cos2α-sin 2α sin 2α= 21(1+ cos2 α) sin 2α= 21(1- cos2 α)

1/3*sin(1/2)*sin(1/2) sin(0.5)*sin(0.5)/3 pow(sin(0.5)，2)/3 1/3.0*pow(sin(1.0.2)，2)

0.5*SIN(1/2)*2 SIN(0.5)**2/2 0.5(SIN(1/2))**2 (SIN**2)(1/2)/2

sin2－cos2 cos2－sin2 ±（sin2－cos2） sin2+cos2

sin α+sin β= 2sin( 2 )cos( 2 ) sin α+sin β= 2cos( 2 )sin( 2 ) sin α+sin β= 2cos( 2 )cos( 2 ) sin α+sin β= 2cos( 2 )sin( 2 )

分析法反证法综合法间接证明法

sin2 α= 2sin α? cos α sin2 α= 21(1- cos2 α) sin2 α= 21(1+ cos2 α) sin2 α= 21sin αcosα

cos α-cos β=- 2sin( 2 )sin( 2 ) cos α-cos β= 2sin( 2 )sin( 2 ) cos α-cos β= -2sin(2)sin(2) cos α-cos β= 2sin( 2 )sin( 2 )

f'(sin²x)sin 2s f'(sin²x) 2sin xf'(sin²x) 2f'(sin²x)

1/3*sin(1/2)*sin(1/2) sin(0.5)*sin(0.5)/3 pow(sin(0.5),2)/3 1/3.0*pow(sin(1.0/2),2)

1/3*sin(1/2)*sin(1/2) sin(0.5)*sin(0.5)/3 pow(sin(0.5)，2)/3 1/3.0*pow(sin(1.0/2)，2)

sin 2 =± 2cos 1 sin 2 = ± 2cos 1 sin 2 =± 2sin 1 sin 2 = ± 2sin 1

sin1sin2sin3sin3

1/3,sin(1/2)*sin(1/2) sin(0.5)*sin(0.5)/3 pow(sin(0.5),2)/3 1/3.0*pow(sin(1.0/2)，2)

1/3*sin(1/2)*sin(1/2) sin(0.5)*sin(0.5)/3 pow(sin(0.5),2)/3 1/3.0*pow(sin(1.0/2),2)