90∘+B290^{\circ}+\frac{B}{2}90∘+2B
90∘−B290^{\circ}-\frac{\mathrm{B}}{2}90∘−2B
90∘+C290^{\circ}+\frac{C}{2}90∘+2C
90∘−C290^{\circ}-\frac{C}{2}90∘−2C
