Chapter 2, Problem 5CR

To determine

Postulate, Property, definition or theorem that justifies the statement.

Answer to Problem 5CR

Substitution property

Explanation of Solution

Given:

  $m\angle A+m\angle B+m\angle C={180}^0,m\angle C={50}^0\text{ then }m\angle A+m\angle B+{50}^0={180}^0$

Let,

  $\begin{array}{l}m\angle A+m\angle B+m\angle C={180}^0\mathrm{........1}\\ m\angle C={50}^0\mathrm{..............2}\end{array}$

Now, substituting the value of equation 2 in equation 1,

  $m\angle A+m\angle B+{50}^0={180}^0$

Therefore, here substitution property is used.