UPSC NDA Math Model Paper 7

Here, the pair of straight lines are 2x + y = 1 and 3x - y = 2
2x + y = 1 ⇒y = -2x + 1 so, m1=−2
And, 3x - y = 2 ⇒y = 3x - 2 so, m2=3
So, angle between given pair of straight lines =θ=tan−1|

m2−m1

1+m1m2

|
=tan−1|

3−(−2)

1+3(−2)

|
=tan−11
Hence, option (1) is correct.