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I'm making an animation in javascript using HTML canvas to simulate Kepler's 2nd Law for a school Project. Here's a link to understand Kepler's Second Law. https://www.windows2universe.org/the_universe/uts/kepler2.html

Kepler's 2nd Law basically states that area of the triangles formed by two pairs of points in time are equal if the time difference between each point is equal.

Additionally, the velocity of the planet around the sun increases when it is closer and decreases when it is farther away. We can relate this by dividing some number by the distance from the sun squared or v = 50000/r^2.

For the animation, I'm using windowRequestAnimationFrame. To achieve the actual animation, I'm using a polar coordinate system. http://mathworld.wolfram.com/PolarCoordinates.html

I modulate the angle by multiplying it by the time object. Then I multiply it by the velocity.

Now on to the actual issue. To have a changing velocity which increases when the planet is closer to the sun and decreases when it is farther away, I need the polar angle to calculate it, however, I'm multiplying the velocity by this angle. How can update the velocity with the changing angle?

I feel as if there is a simple solution that I can't grasp. I have the link to my full code which is fully functional and can be run in a browser.
https://drive.google.com/file/d/1EoDgzoSVFDJ-hJMXuA47rBwjQ9vMQFbD/view?usp=sharing

Thank you for your consideration.

    // Initial Angle Values



    var Ang1 = Math.PI;

    var Ang2 = 2 * Math.PI;







  // Initial Distances from the center of the ellipse



    var distance = Distance(Ang1)

    var distance2 = Distance(Ang2)



// X,Y coordinates derived from the distance using sin,cos functions



    var line1_x = orbit.centerx +(distance *  Math.cos(Ang1))

    var line1_y = orbit.centery +(distance *  Math.sin(Ang1))

    var line3_x = orbit.centerx +(distance2 *  Math.cos(Ang2))

    var line3_y = orbit.centery + (distance2 *  Math.sin(Ang2))





// Initial Distance from the sun using the distance formula

    var focalDistance1 = coordDistance(line1_x,line1_y,sun_x,sun_y)

    var focalDistance2 = coordDistance(line3_x,line3_y,sun_x,sun_y)





// Initial velocityies calculated using distance from the sun

    var velocity1 = 50000/Math.pow(focalDistance1,2)

    var velocity2 = 50000/Math.pow(focalDistance2,2)



















// Multiplying the initial angles by time to animate and velocity to speed up

    var orbitAngle = ((Ang1/60)*time.getSeconds() + (Ang1/60000)* time.getMilliseconds())* velocity1;

    var orbitAngle3 = ((Ang2/60)*time.getSeconds() + (Ang2/60000)* time.getMilliseconds())* velocity2;



// The polar angle coords of the point ahead by the time interval, multiplying by time to animate and velocity to speed up

    var orbitAngle2 = (   ((Ang1/60) * (time.getSeconds()+timeInterval)) + ((Ang1/60000)*(time.getMilliseconds()+timeInterval*1000))) * velocity1;

    var orbitAngle4 = ( ((Ang2/60) * (time.getSeconds()+timeInterval)) + ((Ang2/60000)*(time.getMilliseconds()+timeInterval*1000))) * velocity2;

















    //Animating time interval positions using distance and angle

    var distance = Distance(orbitAngle)

    var distance2 = Distance(orbitAngle2)

    var distance3 = Distance(orbitAngle3)



    var distance4 = Distance(orbitAngle4)







    var line1_x = orbit.centerx +(distance *  Math.cos(orbitAngle))

    var line1_y = orbit.centery +(distance *  Math.sin(orbitAngle))

    var line2_x = orbit.centerx +(distance2 *  Math.cos(orbitAngle2))

    var line2_y = orbit.centery + (distance2 *  Math.sin(orbitAngle2))



    var line3_x = orbit.centerx + (distance3 *  Math.cos(orbitAngle3))

    var line3_y = orbit.centery + (distance3 *  Math.sin(orbitAngle3))

    var line4_x = orbit.centerx +(distance4 *  Math.cos(orbitAngle4))

    var line4_y = orbit.centery + (distance4 *  Math.sin(orbitAngle4))





    var focalDistance1 = coordDistance(line1_x,line1_y,sun_x,sun_y);

    var focalDistance2 = coordDistance(line3_x,line3_y,sun_x,sun_y);



    var velocity1 = 50000/Math.pow(focalDistance1,2)

    var velocity2 = 50000/Math.pow(focalDistance2,2)