ATAN( )

Topic group Related topics

Returns the inverse tangent (arctangent) of a number.

Syntax

ATAN(<expN>)

<expN>

Any positive or negative number representing the tangent of an angle.

Description

ATAN( ) returns the radian value of the angle whose tangent is <expN>. ATAN( ) returns a number from –pi/2 to pi/2 radians. ATAN( ) returns 0 when <expN> is 0. For values of x from –pi/2 to pi/2, ATAN(y) returns x if TAN(x) returns y.

To convert the returned radian value to degrees, use RTOD( ). For example, if the default number of decimal places is 2, ATAN(1) returns 0.79 radians, while RTOD(ATAN(1)) returns 45.00 degrees.

Use SET DECIMALS to set the number of decimal places ATAN( ) displays.

ATAN( ) differs from ATN2( ) in that ATAN( ) takes the tangent as the argument, but ATN2( ) takes the sine and cosine as the arguments.

To find the arccotangent of a value, subtract the arctangent of the value from pi/2. For example, the arccotangent of 1.73 is PI/2 – ATAN(1.73), or .52.