I've been having a bit of trouble with geometry proofs. I'm really trying to learn and figure this one out myself, but I could use a little guidance. I'm not sure if I'm missing steps or just making a huge mistake without noticing. If someone could look it over and tell me what I should fix/improve, that would be great.

Prove: If an isosceles triangle has an altitude from the vertex to the base, then

**the altitude bisects the vertex angle.**
Given: Triangle ABC is isosceles; CD is the altitude to base AB.

**note what you are trying to prove **
Proof:

1. Triangle ABC is isosceles. - Given

2.

AC is congruent to

BC - definition of isosceles triangle

3. CD is altitude to base AB - given

4. <C

DA and <CDB are congruent right angles - definition of altitude

5. CD is congruent to CD - reflexive property

6. Triangle CDA is congruent to triangle CDB - hypotenuse-leg theorem

7. angle ACD is congruent to angle BCD ... cpctc 8. CD bisects the vertex angle ACB ... def. of an angle bisector