tan2α
=tan[(α+β)+(α-β)]
=[tan(α+β)+tan(α-β)]/[1-tan(α+β)(α-β)]
=-4/7
tan2β
=tan[(α+β)-(α-β)]
=[tan(α+β)-tan(α-β)]/[1+tan(α+β)(α-β)]
=-1/8
tan2α
=tan[(α+β)+(α-β)]
=[tan(α+β)+tan(α-β)]/[1-tan(α+β)(α-β)]
=-4/7
tan2β
=tan[(α+β)-(α-β)]
=[tan(α+β)-tan(α-β)]/[1+tan(α+β)(α-β)]
=-1/8