Sin3A/sinA-cos3A/cosA=2 求证明,
问题描述:
Sin3A/sinA-cos3A/cosA=2 求证明,
答
Sin3A/sinA-cos3A/cosA
=(sin3AcosA-cos3AsinA)/(sinAcosA)
=sin(3A-A)/(sinAcosA)
=sin2A/(sinAcosA)
=2sinAcosA/(sinAcosA)
=2