Plane Geometry

Let us start from a simple question. This is more to learn on how to study a question. By having this skill, students will not need to worry about any kind of question.

ABC and DBC are equilateral triangles. Prove that
Think:
Whenever we attempt to a question, we should start from all the information given in the question and form a complete diagram from it.

Information we can get from the question:
equilateral triangle: means all 3 sides have same length, and all 3 angles included are the same.

Answer:
For those angles that we need to prove, first let them as an unknown for easier in visualization.


As ABC and DBC are equilateral triangles, and both triangles share BC,
AC = CD

EC is side shared by triangle EAC and triangle EDC.
Therefore, Triangle EAC and triangle EDC are congruent (SAS).