The Math.acos function finds the angle in radians from a cosine value in JavaScript. It gives a value between 0 and π. JavaScript uses this to help with trigonometry.
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JavaScript Math.acos helps measure angles and you don’t need a calculator. You can use it with numbers from -1 to 1. JavaScript Math.acos returns results you can trust every time.
How Math.acos Works in JavaScript
JavaScript Math.acos returns the arc cosine of a number. The value must be between -1 and 1. The result is in radians, not degrees. The output is a number between 0 and π.
The syntax looks like this:
Math.acos(x)x: A number from -1 to 1.- Return value: A number between 0 and π (in radians).
Let me explain the details. Math.acos looks at a cosine value. It finds the angle that matches it. The angle is in radians. It does not round or convert. It gives the exact result.
Use Math.acos when you need to find an angle based on a cosine value. It works well in geometry. You can also use it for animation or when you rotate shapes.
Take this example to understand better:
Math.acos(0.5)This returns a value close to 1.047. That means the angle is about 60 degrees. The function looks at the cosine value (0.5). It gives you the angle in radians that matches it. This helps you reverse a cosine operation.
Examples of JavaScript Math.acos
Basic angle from 0.5 cosine
Math.acos(0.5)This returns about 1.047. That equals 60 degrees in radians. It shows how JavaScript gets the angle from a cosine value. The input is inside the allowed range.
Use -1 to get full π
Math.acos(-1)This returns 3.14159265. That is π. This is the highest value Math.acos can return. The cosine of π equals -1, so this works in reverse.
Use 1 to get zero
Math.acos(1)This returns 0. The cosine of 0 is 1, so Math.acos(1) gives 0 back. You now see the lowest output.
Check a value out of range
Math.acos(2)This returns NaN. The input is too large. JavaScript cannot find an angle with cosine of 2. This shows how Math.acos works only within the allowed range.
Use with Math.cos to reverse
Math.acos(Math.cos(2))This returns 2. Math.cos(2) finds the cosine. Then Math.acos reverses it and gives the same angle back. This shows how both functions connect.
Use inside a full formula
let sideA = 3;
let sideB = 4;
let sideC = 5;
let angleC = Math.acos((sideA**2 + sideB**2 - sideC**2) / (2 * sideA * sideB));This finds the angle between sideA and sideB. It applies the law of cosines to do that. The formula works for triangles. Math.acos gives the angle in radians. This helps with geometry problems.
Browser and JavaScript Version Support
Compatibility Across Browsers
- Chrome supports Math.acos from version 1.
- Firefox supports it from version 1.
- Safari supports it from version 1.
- Edge and Internet Explorer support it from early versions.
Support in Older JavaScript Versions
- Math.acos exists from ES1.
- It works in all JavaScript versions after that.
- It does not need extra setup.
- It does not break in modern browsers.
Math.acos runs well across all major browsers. You can use it without any extra code. It works the same way in old and new projects.
Wrapping Up
In this article, you learned how JavaScript Math.acos works. You also saw how to use it and what result it gives.
Here’s a quick recap:
- JavaScript Math.acos finds the arc cosine of a number.
- The input must be between -1 and 1.
- The result comes in radians.
- You get values between 0 and π.
- Use it to find angles from cosine values.
- It does not work if the input is outside the range.
- It works with all JavaScript versions.
- All major browsers support it.
- It works well in geometry and rotation.
- You can reverse cosine values with it.
