Cos-1 Calculator - Inverse Cosine (Arccosine)

Your details

Switch between entering a raw cosine value or two triangle side lengths.
A number between -1 and 1. The calculator returns the angle whose cosine equals x.
Angle (degrees)Acute (up to 90 deg)
60deg

The arccosine result in degrees

Angle (radians)1.047198rad
Radians (exact)pi/3
60 deg
Acute (0-90 deg)<90Obtuse (90-180 deg)90+

arccos(0.5000) = 60.0000 degrees

  • This is an exact standard angle: 60 degrees.
  • To verify: cos(60.0000 deg) = 0.500000, which rounds to your input.
  • The angle is acute, meaning it fits inside a right triangle.
  • In radians, this equals pi/3 (exact fraction form).

Next stepTo find the cosine of an angle, use the forward cosine function. For the other two unknowns in a right triangle, switch to triangle mode above.

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