Theorem
If a line bisects the vertex angle of an isosceles triangle, then the line is also the perpendicular bisector of the base.
If …
Then …
You will prove Theorem 4-5 in Exercise 26.
GRIDDED RESPONSE
What is the value of x?
What does the diagram tell you?
Since
Since
Since
A corollary is a theorem that can be proved easily using another theorem. Since a corollary is a theorem, you can use it as a reason in a proof.
Corollary
If a triangle is equilateral, then the triangle is equiangular.
If …
Then …
Corollary
If a triangle is equiangular, then the triangle is equilateral.
If …
Then …