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Arccos (inverse cosine, cos⁻¹) returns the angle whose cosine equals the input value. The output is in the range [0°, 180°] or [0, π] radians.

公式

θ = arccos(x) where cos(θ) = x
x
input value (cosine) — must be in range [−1, 1]
θ
angle result (degrees or radians)

ステップバイステップガイド

  1. 1arccos(x) returns θ where cos(θ) = x
  2. 2Domain: x ∈ [−1, 1]
  3. 3Range: [0°, 180°] or [0, π] radians
  4. 4arccos(0.5) = 60°, arccos(−1) = 180°

解いた例

入力
arccos(0.5)
結果
60° or π/3 radians
入力
arccos(0)
結果
90° or π/2 radians
入力
arccos(−0.5)
結果
120° or 2π/3 radians

よくある質問

What is the domain and range of arccos?

Domain: [−1, 1]. Range: [0°, 180°] or [0, π] radians.

Why is arccos(1) = 0 and arccos(−1) = 180°?

cos(0°) = 1, so the angle whose cosine is 1 is 0°. Similarly, cos(180°) = −1.

Is arccos the same as 1/cos?

No! arccos is the inverse function (angle from cosine). 1/cos is the reciprocal (secant).

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