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/*
Returns the sum of a geometric progression
Article on Geometric Progression: https://en.wikipedia.org/wiki/Geometric_series
Examples:
> sumOfGeometricProgression(2, 0.5, 6)
3.9375
> sumOfGeometricProgression(0.5, 10, 3)
55.5
> sumOfGeometricProgression(0.5, 10, Infinity)
Error: The geometric progression is diverging, and its sum cannot be calculated
*/
/**
*
* @param {Number} firstTerm The first term of the geometric progression
* @param {Number} commonRatio The common ratio of the geometric progression
* @param {Number} numOfTerms The number of terms in the progression
*/
function sumOfGeometricProgression(firstTerm, commonRatio, numOfTerms) {
if (!Number.isFinite(numOfTerms)) {
/*
If the number of Terms is Infinity, the common ratio needs to be less than 1 to be a convergent geometric progression
Article on Convergent Series: https://en.wikipedia.org/wiki/Convergent_series
*/
if (Math.abs(commonRatio) < 1) return firstTerm / (1 - commonRatio)
throw new Error(
'The geometric progression is diverging, and its sum cannot be calculated'
)
}
if (commonRatio === 1) return firstTerm * numOfTerms
return (
(firstTerm * (Math.pow(commonRatio, numOfTerms) - 1)) / (commonRatio - 1)
)
}
export { sumOfGeometricProgression }