diff --git a/Maths/BisectionMethod.js b/Maths/BisectionMethod.js
index 49b8c8ecc0..4539e6d466 100644
--- a/Maths/BisectionMethod.js
+++ b/Maths/BisectionMethod.js
@@ -23,7 +23,7 @@ const findRoot = (a, b, func, numberOfIterations) => {
// Bolzano theorem
const hasRoot = (a, b, func) => {
- return func(a) * func(b) < 0
+ return func(a) * func(b) <= 0
}
if (hasRoot(a, b, func) === false) {
throw Error(
@@ -45,10 +45,9 @@ const findRoot = (a, b, func, numberOfIterations) => {
const prod2 = fm * func(b)
// Depending on the sign of the products above, decide which position will m fill (a's or b's)
- if (prod1 > 0 && prod2 < 0) return findRoot(m, b, func, --numberOfIterations)
- else if (prod1 < 0 && prod2 > 0)
- return findRoot(a, m, func, --numberOfIterations)
- else throw Error('Unexpected behavior')
+ if (prod2 <= 0) return findRoot(m, b, func, --numberOfIterations)
+
+ return findRoot(a, m, func, --numberOfIterations)
}
export { findRoot }
diff --git a/Maths/test/BisectionMethod.test.js b/Maths/test/BisectionMethod.test.js
index ad865b6ad6..4a49e8f6a4 100644
--- a/Maths/test/BisectionMethod.test.js
+++ b/Maths/test/BisectionMethod.test.js
@@ -1,14 +1,7 @@
import { findRoot } from '../BisectionMethod'
test('Equation f(x) = x^2 - 3*x + 2 = 0, has root x = 1 in [a, b] = [0, 1.5]', () => {
- const root = findRoot(
- 0,
- 1.5,
- (x) => {
- return Math.pow(x, 2) - 3 * x + 2
- },
- 8
- )
+ const root = findRoot(0, 1.5, (x) => x ** 2 - 3 * x + 2, 8)
expect(root).toBe(0.9990234375)
})
@@ -35,3 +28,12 @@ test('Equation f(x) = sqrt(x) + e^(2*x) - 8*x = 0, has root x = 0.93945851 in [a
)
expect(Number(Number(root).toPrecision(8))).toBe(0.93945851)
})
+
+test('Equation f(x) = x^3 = 0, has root x = 0.0 in [a, b] = [-1.0, 1.0]', () => {
+ const root = findRoot(-1.0, 1.0, (x) => x ** 3, 32)
+ expect(root).toBeCloseTo(0.0, 5)
+})
+
+test('Throws an error when function does not change sign', () => {
+ expect(() => findRoot(-1.0, 1.0, (x) => x ** 2, 10)).toThrowError()
+})
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