I can use theorems about isosceles and equilateral triangles.
http://www.regentsprep.org/regents/math/geometry/gp6/pracisos.htm
Source: www.regentsprep.org
http://www.ixl.com/math/geometry/proofs-involving-isosceles-triangles
Source: www.ixl.com
http://www.ixl.com/math/geometry/congruency-in-isosceles-and-equilateral-triangles