Inverse Cosine (arccos) Calculator
The Inverse Cosine (arccos) Calculator finds the angle whose cosine equals a value between -1 and 1, shown in both degrees and radians. The formula used is: arccos(x) = the angle θ such that cos(θ) = x, with the result in [0°, 180°].
Formula
arccos(x) = the angle θ such that cos(θ) = x, result in [0°, 180°]
Example Calculation
Inputs
- Value (−1 to 1): 0.5
arccos(0.5) = 60° (π/3 ≈ 1.0472 radians), because cos(60°) = 0.5.
Frequently asked questions
What is arccos?
Arccos, the inverse cosine, returns the angle whose cosine equals the value you enter. It reverses the cosine function.
What input range is allowed?
Only values from -1 to 1, since cosine never produces a result outside that range.
What is the output range?
The principal value runs from 0° to 180° (0 to π radians).
How do I get radians instead of degrees?
This calculator shows both. To convert manually, multiply the degree result by π/180.
Why does arccos(0.5) equal 60°?
Because cos(60°) = 0.5, so the angle whose cosine is 0.5 is 60°.