# Did I do the following two column proof correctly?

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• Jul 3rd 2007, 05:42 PM
icebreaker09
Did I do the following two column proof correctly?
Attachment 3487

Here' what I came up with:

Given: \$\displaystyle \angle SRT = \angle STR\$; \$\displaystyle \angle 3 = \angle 4\$
Prove: \$\displaystyle \angle 1 = \angle 2\$

Statements:
1. \$\displaystyle \angle SRT = \angle STR\$; \$\displaystyle \angle 3 = \angle 4\$

2. \$\displaystyle \angle 1 + \angle 3 = \angle SRT\$; \$\displaystyle \angle = 2 + \angle 4 = \angle STR\$

3. \$\displaystyle \angle 1 + \angle 3 = \angle 2 + \angle 4\$

4. \$\displaystyle \angle 1 = \angle 2\$

Reasoning:
1. Given

2. Angle addition postulate

3. Addition property of equality

4. Substitution

Am I right?
• Jul 3rd 2007, 06:28 PM
Quick
All the steps I added have red numbers. The things I changed are in red as well.

Statements:
1. \$\displaystyle \angle SRT = \angle STR\$; \$\displaystyle \angle 3 = \angle 4\$

2. \$\displaystyle \angle 1 + \angle 3 = \angle SRT\$; \$\displaystyle \angle 2 + \angle 4 = \angle STR\$

3. \$\displaystyle \angle 2+\angle 4=\angle SRT\$

4. \$\displaystyle \angle 1 + \angle 3 = \angle 2 + \angle 4\$

5.
\$\displaystyle \angle 1 +\angle 3 = \angle 2 +\angle 3\$

6. \$\displaystyle \angle 1 = \angle 2\$

Reasoning:
1. Given

2. Angle addition postulate

3.
Transitive property (or Substitution)

4. Transitive Property (or Substitution)

5. Substitution

6. Subtraction property of equality
• Jul 3rd 2007, 06:30 PM
Quick
To other helpers:

Does anyone else use the transitive property? Or was that just my teacher...
• Jul 3rd 2007, 06:45 PM
ThePerfectHacker
Quote:

Originally Posted by Quick
Does anyone else use the transitive property?

I use "transitive" because "substitution" is not well-defined for me. :D