Q.

The direction in which a straight line must be drawn through the point (1, 2) so that its point of intersection with the line x+y=4 may be at a distance 63 from this point is

1 30°, 60°  
2 15°, 75°  
3 ∥ to x-axis  
4 ∥ to y-axis  

Ans.

(2)

x-1cosθ=y-2sinθ=r=63=23

The point (rcosθ+1, rsinθ+2) lies on x+y=4

∴  r(cosθ+sinθ)=1

or  cosθ+sinθ=32  or  12cosθ+12sinθ=32

or  cos(θ-45°)=cos30°

∴  θ-45°=±30°

∴  θ=75°, 15°.