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cos(2x)
1-sin²x, 2cos²x-1, cos²x-sin²x
sin(2x)
2sinxcosx
trigettan
1=sin²x+cos²x
sin(x+u)
sinxcosu+sinucosx
sin(x-u)
sinxcosu-sinucosx
cos(x+u)
cosxcosu-sinxsinu
cos(x-u)
cosxcosu+sinxsinu
asinx+bcosx
csin(x+v) där c=(a²+b²)^1/2