400
Prove the vertical angle theorem
What is
1.<1 and <2 are linear pair ...... given
2.<2 and <3 are linear pair ......given
3.m<1 + m<2=180 ...... definition of supplementary angles
4.m<2 + m<3=180 ...... definition of supplementary angles
5.m<1 + m<2=m<2 + m<3......substitution prop
6. m<1 =m<2 ...... subtraction prop
7. <1 ≅<2...... Transitive property QED