cos2π/3(sin3π/5+icos3π/5)的三角式是

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cos2π/3(sin3π/5+icos3π/5)的三角式是cos2π/3(sin3π/5+icos3π/5)的三角式是cos2π/3(sin3π/5+icos3π/5)的三角式是原式=-cos2π/

cos2π/3(sin3π/5+icos3π/5)的三角式是
cos2π/3(sin3π/5+icos3π/5)的三角式是

cos2π/3(sin3π/5+icos3π/5)的三角式是
原式=-cos2π/3[-sin3π/5-icos3π/5]
=1/2*[-cosπ/10+isinπ/10]
=1/2*(cos9π/10+isin9π/10)

cos(2π/5) = cos72°
cos90°0sin(3π) = sin(2π+π) = sinπ = 0
tan(2π/5) = tan72°
tan0°0cos72°,并且cos72°<1
∴tan72°>1
综合:tan(2π/5)>cos(2π/5)>sin(3π)