Find the equation of straight line at a perpendicular distance of 4 units from the origin and making an angle of 120° with the +ve direction of x-axis measured anticlockwise.
Given p = 4 θ = 120°, also θ= 90° +α
∴120° = 90° + α
or α = 30°
∴By normal form of straight line, the equation of required straight line will y be x cos30° +ysin30° = 4
