---
title: "ClikaRT::ops::acos"
sidebar_label: "acos"
description: "Elementwise arccosine. \\[ \\cos^{-1}(x_i) \\] Inputs outside [-1, 1] produce NaN. Value-domain violations follow IEEE semantics (NaN / ±inf in the result), never an error."
---

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<span class="api-kind api-kind--function">function</span>

## acos() {#acos}

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[`Tensor`](../Tensor.md) **`acos`**([`Tensor`](../Tensor.md) `input`)

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Elementwise arccosine.

$$
\cos^{-1}(x_i)
$$

Inputs outside `[-1, 1]` produce NaN. Value-domain violations follow IEEE semantics (NaN / ±inf in the result), never an error.

**Throws**

- `ClikaRT::Error`: when the input's dtype is not served for this operation (the machine-readable reason rides `code_name()`).

**Returns:** a new tensor, same shape and dtype as `input`.

```cpp
auto y = ClikaRT::ops::acos(x);
```

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Declared in `ClikaRT/compute/ops.h`, line 4808

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