Draw circle with radians

We know that the angle will not change with the radius. Angle, arc length (or area) and radius are inevitably related.
Because the arc length and radius are numbers. The angle is that the degree conversion is not very convenient. If we can directly represent the relationship F by the arc length and radius, it is more convenient. Therefore, we have the concept of radians.
The unit of radians is recorded as rad. Radians are the arc-length ratio radius, that is, L/R. If l = r, it indicates 1rad.
The circumference of one circle is L = pI * 2 * r. The circumference/R of a circle is a radian, and L/r = 2 * pI * r/r = 2 * pI <=> 360 degrees. therefore, a circle can be expressed either in 360 degrees or in 2 * PI radians. 2 * PI rad.
1rad = 180/PI = 57.3 degrees. 1 degree = PI/180 = 01745rad.
The trigonometric function decodes the relationship between the degree and the two sides.
Use the trigonometric function below to draw a circle.

VaRC = Document. getelementbyid ("mycanvas ");
VaRCxt = C. getcontext ("2D ");
VaRR = 100;

Cxt. moveTo (200,100 );
For(VaRI1 = 0; I1 <= 360; I1 ++)
Cxt. lineto (R + math. Cos (fmath. radian (I1) * R, r-Math.sin (fmath. radian (I1) * R );
Cxt. Stroke ()

Click here to view the source code