Geometric Proofs

harpazo

I was placed in modified math classes throughout most of the high school years based on my poor academic background. I will not go into detail here. Based on this situation, I never took regular math classes in high school. Thus, I never learned direct and indirect geometric proofs using the Statement versus Reason chart. Does any here know the best way to learn geometric proofs at the high school level? I graduated from high school in 1984. By graduated I mean, I was promoted from grade to grade without having earned the promotion, which is very common in NYC public schools.

harpazo

I found this online:

direct proof: go from assumptions to conclusion.

indirect proof: assume the opposite, derive a contradiction

ΔABC, ΔDEF
len(AB) = len(DE)
m(∠B) = m(∠E)
len(BC) = len(EF)

prove len(AC) = len(DF)

2 column proof
statement | reason
len(AB) = len(DE) | given
m(∠B) = m(∠E) | given
len(BC) = len(EF) | given

ΔABC≅ΔDEF | congruent by SAS
{side angle side}

len(AC) = len(DF) | CPCT
{corresponding parts of congruent triangles (are congruent)}

QED

It makes zero sense to me.

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