25 lines
719 B
Markdown
25 lines
719 B
Markdown
---
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title: vectorAngle
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tags: math,beginner
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firstSeen: 2019-12-16T16:43:13+02:00
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lastUpdated: 2021-01-08T00:23:44+02:00
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---
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Calculates the angle (theta) between two vectors.
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- Use `Array.prototype.reduce()`, `Math.pow()` and `Math.sqrt()` to calculate the magnitude of each vector and the scalar product of the two vectors.
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- Use `Math.acos()` to calculate the arccosine and get the theta value.
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```js
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const vectorAngle = (x, y) => {
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let mX = Math.sqrt(x.reduce((acc, n) => acc + Math.pow(n, 2), 0));
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let mY = Math.sqrt(y.reduce((acc, n) => acc + Math.pow(n, 2), 0));
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return Math.acos(x.reduce((acc, n, i) => acc + n * y[i], 0) / (mX * mY));
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};
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```
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```js
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vectorAngle([3, 4], [4, 3]); // 0.283794109208328
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```
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