Loan calculator and amortization schedule

main.go

package main

import (
	"fmt"
	"math"
)

func main() {
	fmt.Println("Loan calculator")
	
	P := 40000.
	APR := 5.5
	years := 15.
	periods := years * 12.
	r := APR / 100. / 12.
	rP := r * P
	rN := math.Pow(1+r, -float64(periods))
	c := (rP / (1 - rN))
	
	fmt.Printf("Payment:    %.2f\n", c)
	fmt.Printf("Total paid: %.2f\n", c*periods)
	fmt.Printf("\n       Amortization Schedule\n\n")
	fmt.Printf(" Mth  %10s %10s %10s\n", "Total", "Principal", "Interest")
	fmt.Println("--------------------------------------")

	for i := 1; i < int(periods) + 1; i++ {		
		interest := (P * r - c) * (math.Pow(1+r, float64(i)) - 1)/r + c*float64(i)
		principal := c*float64(i) - interest
		
		fmt.Printf("[%03d] %10.2f %10.2f %10.2f\n", i, c*float64(i), principal, interest)
	}
}