Which of the following is the best definition of a linear pair of angles?
1) A pair of supplementary angles is called a linear pair.
2) A pair of adjacent angles whose sum is equal to 180°.
Answer: Linear pair is defined as a pair of adjacent angles whose sum is equal to 180°. Thus, Option 2) is correct.
Let us understand the definition of a linear pair of angles.
Linear pair angles are formed by two intersecting lines. The pair is adjacent and their sum is equal to 180°.
Look at the figure shown below. ∠1 and ∠2 form a pair of linear angles.
i.e, ∠1 + ∠2 = 180°
But every pair of supplementary angles can't be a linear pair. Look at the figure shown below. The angles 75° and 105° form a pair of supplementary angles but they do not form a linear pair because they are not adjacent.