Instruction Active
Writing a Two-Column Proof
Try it
Angles Reasons
Given: ZABC e ZDEF and
ZGHS ZDEF
Prove: m ZABC = mZGHI
LABC
ZDEF
ZGHI
mZABC
x
mZGHI
Statements
✓ 1. LABC - ZDEF
✓ 2. ZGHI ZDEF
3. ZDEF - ZGHI
4. ZABC - ZGHI
Reasons
1. given
2. given
3. symmetric property
4. transitive property
Demo

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?