In Fig. 5.28, PQ || RS. If ∠1 = (2a + b)° and ∠6 = (3a–b)°, then the measure of ∠2 in terms of b is
∠1 = (2a + b)° …Equation (i)
∠6 = (3a–b)°
Since ∠5 and ∠6 forms a linear pair so
∠5 = (180-3a + b)°
∠5 = ∠1 = (180-3a + b)° (Corresponding angles) …Equation (ii)
Equating Equation (i) and Equation (ii) we get
2a + b = 180-3a + b
⇒ 5a = 180
⇒ a = 360
Since ∠1 and ∠2 forms a linear pair so
∠2 = 1800- 2a-b
⇒ ∠2 = (108-b)0