Q.

The angle between the lines 2x-y+3=0 and x+2y+3=0 is

1 90°  
2 60°  
3 45°  
4 30°  

Ans.

(1)

Given equations of lines are

2x-y+3=0;    m1=slope=2

x+2y+3=0;    m2=slope=-12

So,  tanθ=|m1-m21+m1m2|=|2+121-1|=52×0=50=∞

⇒  tanθ=tanπ2⇒θ=π2