Line Equation with angle

Question

How can I find equation of a line or draw a line, given a starting point, length of line and angle of line (relative to x-axis)?

Answer 1

Let's call the start point (x1, y1) the other end of the line (x2, y2).

Then if you are given a length [L] and an angle from the x-axis [a]:

x2 = x1 + (L * cos(a))

y2 = y1 + (L * sin(a))

If the angle is from the y-axis - swap the cos and the sin.

Draw your line from (x1,y1) to (x2, y2).

You may find an ambiguity as to which direction you want the line to go, you need to be careful how you define your angle.