sinα ·cosβ=0.5[sin(α+β)+sin(α-β)]
cosα ·sinβ=0.5[sin(α+β)-sin(α-β)]
cosα ·cosβ=0.5[cos(α+β)+cos(α-β)]
sinα ·sinβ=-0.5[cos(α+β)-cos(α-β)]
sinα ·cosβ=0.5[sin(α+β)+sin(α-β)]
cosα ·sinβ=0.5[sin(α+β)-sin(α-β)]
cosα ·cosβ=0.5[cos(α+β)+cos(α-β)]
sinα ·sinβ=-0.5[cos(α+β)-cos(α-β)]