Arccos calculator
Find the principal angle whose cos is x. Results are 0° to 180°, shown in degrees and radians.
Formula
θ = arccos(x); cos(θ) = x; degrees = radians × 180/π.
Angle (radians) ≈ pi÷2-atan((0.5)÷sqrt(1-(0.5)^2)) · Angle (degrees) ≈ (1.047197551)×180÷pi
How to use
- Enter the ratio x.
- Keep x from −1 to 1.
- Read the principal angle.
Examples
- arccos(0.5) = 60°.
Frequently asked questions
What does inverse mean?
It finds an angle from its cos value; it is not 1/cos(x).
Which angle is returned?
The principal angle, 0° to 180°.
Is the input an angle?
No. x is a unitless ratio in [−1,1].
Sources
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