The math Package

The math package provides numeric functions and constants for floating-point calculations.

math.Sqrt computes a square root, math.Pow computes powers, and math.Abs obtains a floating-point magnitude. Functions such as Sqrt usually operate on float64, so integer variables may require explicit conversion.

Floating-point values are approximations; direct equality is often inappropriate for calculated results. The math package’s Pi constant can be used in geometric formulas.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import (
	"fmt"
	"math"
)

func main() {
	radius := 3.0
	area := math.Pi * math.Pow(radius, 2)
	fmt.Printf("Area: %.2f\n", area)
	fmt.Println("Square root:", math.Sqrt(81))
}

Output

Area: 28.27
Square root: 9

Pow computes radius squared and Pi multiplies it to form a circle’s area, displayed to two decimal places. Sqrt(81) evaluates to 9.

• math.Sqrt returns float64 rather than int.
• Do not use direct == for most approximate floating-point calculations.

Compute the circumference of a radius-5 circle using math.Pi and print two decimals.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced The math Package in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.