Arccosine (arccos or cos⁻¹) is the inverse of the cosine function. Given a value x, arccos(x) returns the angle θ such that cos(θ) = x. The output angle lies in the range [0°, 180°] (or [0, π] radians).

Why must the input be between -1 and 1?

The cosine of any angle always produces a value in [-1, 1]. Therefore the inverse operation is only defined for inputs in that range. Values outside it have no real-number solution.

How do I convert the result from radians to degrees?

Multiply the radian value by 180/π (approximately 57.2958). The calculator does this automatically and shows both units side by side.

What is the difference between arccos and cos⁻¹?

They are the same function. "cos⁻¹" is the notation used on most calculators, while "arccos" is the conventional mathematical notation. Both mean the inverse cosine.

How does arccos differ from arcsin?

Both take inputs in [-1, 1], but their output ranges differ. Arcsin returns angles in [-90°, 90°], while arccos returns angles in [0°, 180°]. They are complementary: arcsin(x) + arccos(x) = 90°.

Can arccos return an angle greater than 180 degrees?

No. By definition the principal value of arccos is restricted to [0°, 180°]. If your problem requires an angle in a different range, you must apply the appropriate supplementary or reflex angle identity manually.

Arccosine Calculator

Name: Arccosine Calculator
Availability: InStock
Author: Nham Vu

Enter a value between -1 and 1 to instantly get its arccosine in both degrees and radians.

Input Value

Value (must be between −1 and 1)

Common values

Result

Enter a value and press Calculate.

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