| **Navigation:**  [[introduction.htm|Language Reference]] > 13 - Built-in Functions >====== ATAN (return arctangent) ====== | [[asin  return arcsine .htm|{{btn_prev_n.gif|Previous page}}]][[introduction.htm|{{btn_home_n.gif|Return to chapter overview}}]][[band  return bitwise and .htm|{{btn_next_n.gif|Next page}}]] |
|  ||

**ATAN(**//expression//**)**

{{blk2blue.jpg|blk2blue.jpg}}

| **ATAN** | Returns inverse tangent. |
| //expression// | A numeric constant, variable, or expression for the value of the tangent. |

The **ATAN** procedure returns the inverse tangent. The inverse of a tangent is the angle that produces the tangent. The return value is the angle in radians. p is a constant which represents the ratio of the circumference and radius of a circle. There are 2p radians (or 360 degrees) in a circle.

| **Return Data Type** | REAL |

**Example:**

**PI        EQUATE(3.1415926535898)     !The value of PI**

**Rad2Deg   EQUATE(57.295779513082)     !Number of degrees in a radian**

**Deg2Rad   EQUATE(0.0174532925199)     !Number of radians in a degree**

** CODE**

** InvTangent = ****ATAN****(TangentAngle)      !Get the Arctangent**

**See Also:**

[[tan  return tangent .htm|TAN]]

[[sin  return sine .htm|SIN]]

[[asin  return arcsine .htm|ASIN]]

[[cos  return cosine .htm|COS]]

[[acos  return arccosine .htm|ACOS]]