Use Math.PI To Calculate Area And Circumference Of A Circle

Introduction

The Math.PI property returns the PI π constant, approximately equal to 3.14159. For example, you can calculate the circumference and surface area of a circle using Math.PI.

console.log(Math.PI);
// 3.141592653589793

Calculating Circumference Of A Circle

Write a function that accepts a number as the circle's radius as the following example:

function circleCircumference(radius) {
  return 2 * Math.PI * radius;
}

console.log(circleCircumference(16));
// 100.53096491487338

Calculating Area Of A Circle

Like the previous example, write a function to calculate the surface area:

function circleArea(radius) {
  return Math.PI * (radius * radius);
}

console.log(circleArea(16));
// 804.247719318987

You can re-write the above function by using the Math.pow() to calculate the radius^2:

function circleArea(radius) {
  return Math.PI * Math.pow(radius, 2);
}

console.log(circleArea(16));
// 804.247719318987

Also read about the Math.ceil() function and Math.floor() function.