Beziers

Bezier curves are very much used in Svg. The quadratic curve
is just that: it draws a curve from outside the arc, as does the mathematical
function.

One is free to specify commands in absolute  - with Q - or relative
terms: with lower case q.

Takes a little getting used to ...

http://blogs.sitepointstatic.com/examples/tech/svg-curves/quadratic-curve.html

http://blogs.sitepointstatic.com/examples/tech/svg-curves/cubic-curve.html

 https://www.w3schools.com/graphics/tryit.asp?filename=trysvg_path2

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Computer graphics use parametric equations to draw; one can
generate a unit circle  (x^2 +y^2 = 1) with a series of sin and cos
functions and cover all gradations more easily. In the case of Beziers',
the one thing one cannot produce is a circle arc, because we are working
with tangents to the curve. Each tangent to a curve is unique and - in the case
of those at the ends of a circle arc - would not meet at the control point.







source: Wikipedia


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In Svg path commands, the first coordinate pair is the starting point of the curve, and
the last, the end-point. In the middles, it is ( if uppercase) the absolute control point;
( for lowercase) the control point relative to start. Below, absolute:

 https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Paths

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 https://youtu.be/2HvH9cmHbG4