△Q△P⋅PQ\mathrm {\dfrac{\triangle Q} {\triangle P} \cdot \dfrac{P}{Q}}△P△Q⋅QP
△P△Q⋅QP\mathrm {\dfrac{\triangle P} {\triangle Q} \cdot \dfrac{Q}{P}}△Q△P⋅PQ
△Q△P⋅QQ\mathrm {\dfrac{\triangle Q} {\triangle P} \cdot \dfrac{Q}{Q}}△P△Q⋅QQ
△P△Q⋅PQ\mathrm {\dfrac{\triangle P} {\triangle Q} \cdot \dfrac{P}{Q}}△Q△P⋅QP
