∠i1=∠i2=∠A2\angle \mathrm{i}_{1}=\angle \mathrm{i}_{2}=\dfrac{\angle \mathrm{A}}{2}∠i1=∠i2=2∠A
2∠i1−δm=∠A2 \angle \mathrm{i}_{1}-\delta_{\mathrm{m}}=\angle \mathrm{A}2∠i1−δm=∠A
∠i1=∠r1\angle \mathrm{i}_{1}=\angle \mathrm{r}_{1}∠i1=∠r1
∠i1+∠r2−δm=∠A2\angle \mathrm{i}_{1}+\angle \mathrm{r}_{2}-\delta_{\mathrm{m}}=\dfrac{\angle \mathrm{A}}{2}∠i1+∠r2−δm=2∠A
