SVG has angle values as: 0 degrees at top, and angle increases clockwise.
General Form: x = rCOS θ y = rSIN θ Javascript θ=degrees: x = length*Math.cos((θ90)*Math.PI/180) y = length*Math.sin((θ90)*Math.PI/180) 

GIVEN: Start point, length, and angle x1= y1= length= angle= x2= y2= 