Scalar projection - finding distance between line and point

[tysonk]

Using a scalar projections how do you show that the distance from a point P(x1,y1) to line
ax + by + c = 0 is

$\frac{|ax1 +b y1 + c|}{\sqrt{a^2 +b^2}}$

I do not know how to approach this, please provide some guidance.

 

[LCKurtz]

Using a scalar projections how do you show that the distance from a point P(x1,y1) to line
ax + by + c = 0 is

$\frac{|ax1 +b y1 + c|}{\sqrt{a^2 +b^2}}$

I do not know how to approach this, please provide some guidance.

Find a normal vector $\hat n$ to the line and a vector $\vec V$ from some point on your line to your given point and think about projections.