Question

What is the reason for Step 3 in the proof below?

Linear Pair Postulate

Angle Addition Postulate

Subtraction Property of Equality

Addition Property of Equality

Answer 1

Linear pair postulate: angles in a straight line sum to `180^o`

Explanation:

In a straight line, the sum of the angles add up to 180; this is known as the "Linear pair postulate"

Since `m/_1` and `m/_2` are in a straight line, their angles must sum to 180. This is the same with `m/_2` and `m/_3`. Therefore,

`m/_1+m/_2=180^o`
`m/_2+m/_3=180^o`