One simple expression that you are most likely to be familiar with thus far is an expression to find the circumference of a circle when you know the radius of the circle. The radius of a circle as you should know is half the diameter of a circle, so by multiplying Math PI times 2 and then multiply again by the radius of a circle, you will get the circumference.
I can not say the use of this expression comes up much in many of the projects that I have worked on thus far. However I do end up working the angles a lot, so lets look at some additional examples of the Math PI constant when working with methods that take radians as an argument.
Another typical expression that might come up would be to get the area of a circle. For this I just need to multiply Math.PI by Math.pow(r, 2) where r is the radius of the circle. The Math.pow method is then another useful method in the math object that will come up in many expressions such as this as a way to square something.
Another interesting expression is that PI can be ascertained by dividing circumference over that of the diameter of a circle. This is one expression that I can not say that I would need to use in projects, but I figured it might be a good one to include in this section just for the heck of it.
The radian is a unit of measurement of angles that can be used as an alternative to degrees. With radians the radius of a circle is used as the unit of measurement for angles, rather than dividing the circumference of a circle by 360. So because the circumference of a circle is equal to 2PIr then this can be used as a way to know how many radians there are in a circle which is 2PI or 6.28… which can be used as a way to work out some methods for conversion.
One use case example of using radians and therefore having a method that uses Math PI to convert degrees to radians would be to have a method that can be used to get a point along the circumference of a circle. I have wrote a pretty lengthly post on the canvas arc method in which I get into the use of these methods as well as the built in canvas methods for drawing a circle.
The method here makes use of the Math.cos, and Math.sin methods booth of which take a radian as the first argument. So if I want to use degrees then I will want to have a method that converts for degrees to radians. So then the method that I covered earlier would come into play with this example then.
In this example I made a simple canvas animation example of a circle bar. That is that it is a circle type of plain progress bar that I often see in all kinds of games and practical projects. This one involves the use of a state object, a method that updates this state object, a method to draw to the canvas, and a main app loop of sorts.
I use Math PI to get the value of Math PI * 2 to which I then use to preform a modulo operation in the update method to make sure that the radian value for the state object is always between 0 and Math PI * 2. In other worlds to make sure that a radian value is between the min and max values for a radian.
So that Math PI constant is there in the Math object for any and all situations in which I would want to use it compared to just using a number literal. However there are situations in which I might want to use a literal, maybe not in number from, but in string form when it comes to making or using some kind of user space project or additional feature that allows for high precision Math.
There is much more to write about, and develop when it comes to use case examples involving the use of Math PI, in time I might get around to updating and expanding this post as more examples come to mind.